diff --git a/.travis.yml b/.travis.yml
index 15c6111..59d59bb 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,3 +3,7 @@ xcode_project: QiniuSDK.xcodeproj
 xcode_scheme: QiniuSDKTests
 xcode_sdk:
   - iphonesimulator7.1
+before_install:
+  - brew update
+  - brew upgrade xctool
+  - gem install cocoapods
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 48b58c9..f93cc3d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 ## CHANGE LOG
 
+### v6.3.3
+
+- [#101] 升级AFNetworking
+
 ### v6.3.2
 
 - [#94] 上传进度指示调整
diff --git a/QiniuSDK/AFNetworking/AFHTTPRequestOperation.m b/QiniuSDK/AFNetworking/AFHTTPRequestOperation.m
index 723a3b3..1de5812 100644
--- a/QiniuSDK/AFNetworking/AFHTTPRequestOperation.m
+++ b/QiniuSDK/AFNetworking/AFHTTPRequestOperation.m
@@ -168,7 +168,7 @@ - (void)pause {
     self.request = mutableURLRequest;
 }
 
-#pragma mark - NSecureCoding
+#pragma mark - NSSecureCoding
 
 + (BOOL)supportsSecureCoding {
     return YES;
@@ -194,7 +194,7 @@ - (void)encodeWithCoder:(NSCoder *)coder {
 #pragma mark - NSCopying
 
 - (id)copyWithZone:(NSZone *)zone {
-    AFHTTPRequestOperation *operation = [[[self class] allocWithZone:zone] initWithRequest:self.request];
+    AFHTTPRequestOperation *operation = [super copyWithZone:zone];
 
     operation.responseSerializer = [self.responseSerializer copyWithZone:zone];
     operation.completionQueue = self.completionQueue;
diff --git a/QiniuSDK/AFNetworking/AFHTTPRequestOperationManager.h b/QiniuSDK/AFNetworking/AFHTTPRequestOperationManager.h
index d7f6d42..9f39029 100644
--- a/QiniuSDK/AFNetworking/AFHTTPRequestOperationManager.h
+++ b/QiniuSDK/AFNetworking/AFHTTPRequestOperationManager.h
@@ -75,12 +75,12 @@
 
  Network reachability status and change monitoring is available through the `reachabilityManager` property. Applications may choose to monitor network reachability conditions in order to prevent or suspend any outbound requests. See `AFNetworkReachabilityManager` for more details.
 
- ## NSecureCoding & NSCopying Caveats
+ ## NSSecureCoding & NSCopying Caveats
 
- `AFHTTPRequestOperationManager` conforms to the `NSecureCoding` and `NSCopying` protocols, allowing operations to be archived to disk, and copied in memory, respectively. There are a few minor caveats to keep in mind, however:
+ `AFHTTPRequestOperationManager` conforms to the `NSSecureCoding` and `NSCopying` protocols, allowing operations to be archived to disk, and copied in memory, respectively. There are a few minor caveats to keep in mind, however:
 
  - Archives and copies of HTTP clients will be initialized with an empty operation queue.
- - NSecureCoding cannot serialize / deserialize block properties, so an archive of an HTTP client will not include any reachability callback block that may be set.
+ - NSSecureCoding cannot serialize / deserialize block properties, so an archive of an HTTP client will not include any reachability callback block that may be set.
  */
 @interface AFHTTPRequestOperationManager : NSObject <NSSecureCoding, NSCopying>
 
diff --git a/QiniuSDK/AFNetworking/AFHTTPRequestOperationManager.m b/QiniuSDK/AFNetworking/AFHTTPRequestOperationManager.m
index 03116cc..4ae7275 100644
--- a/QiniuSDK/AFNetworking/AFHTTPRequestOperationManager.m
+++ b/QiniuSDK/AFNetworking/AFHTTPRequestOperationManager.m
@@ -213,7 +213,7 @@ - (NSString *)description {
     return [NSString stringWithFormat:@"<%@: %p, baseURL: %@, operationQueue: %@>", NSStringFromClass([self class]), self, [self.baseURL absoluteString], self.operationQueue];
 }
 
-#pragma mark - NSecureCoding
+#pragma mark - NSSecureCoding
 
 + (BOOL)supportsSecureCoding {
     return YES;
diff --git a/QiniuSDK/AFNetworking/AFHTTPSessionManager.m b/QiniuSDK/AFNetworking/AFHTTPSessionManager.m
index 5abfe7e..6413297 100644
--- a/QiniuSDK/AFNetworking/AFHTTPSessionManager.m
+++ b/QiniuSDK/AFNetworking/AFHTTPSessionManager.m
@@ -109,23 +109,11 @@ - (NSURLSessionDataTask *)GET:(NSString *)URLString
                       success:(void (^)(NSURLSessionDataTask *task, id responseObject))success
                       failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure
 {
-    NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:@"GET" URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:nil];
+    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"GET" URLString:URLString parameters:parameters success:success failure:failure];
 
-    __block NSURLSessionDataTask *task = [self dataTaskWithRequest:request completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *error) {
-        if (error) {
-            if (failure) {
-                failure(task, error);
-            }
-        } else {
-            if (success) {
-                success(task, responseObject);
-            }
-        }
-    }];
+    [dataTask resume];
 
-    [task resume];
-
-    return task;
+    return dataTask;
 }
 
 - (NSURLSessionDataTask *)HEAD:(NSString *)URLString
@@ -133,23 +121,15 @@ - (NSURLSessionDataTask *)HEAD:(NSString *)URLString
                        success:(void (^)(NSURLSessionDataTask *task))success
                        failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure
 {
-    NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:@"HEAD" URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:nil];
-
-    __block NSURLSessionDataTask *task = [self dataTaskWithRequest:request completionHandler:^(NSURLResponse * __unused response, id __unused responseObject, NSError *error) {
-        if (error) {
-            if (failure) {
-                failure(task, error);
-            }
-        } else {
-            if (success) {
-                success(task);
-            }
+    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"HEAD" URLString:URLString parameters:parameters success:^(NSURLSessionDataTask *task, __unused id responseObject) {
+        if (success) {
+            success(task);
         }
-    }];
+    } failure:failure];
 
-    [task resume];
+    [dataTask resume];
 
-    return task;
+    return dataTask;
 }
 
 - (NSURLSessionDataTask *)POST:(NSString *)URLString
@@ -157,23 +137,11 @@ - (NSURLSessionDataTask *)POST:(NSString *)URLString
                        success:(void (^)(NSURLSessionDataTask *task, id responseObject))success
                        failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure
 {
-    NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:@"POST" URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:nil];
-
-    __block NSURLSessionDataTask *task = [self dataTaskWithRequest:request completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *error) {
-        if (error) {
-            if (failure) {
-                failure(task, error);
-            }
-        } else {
-            if (success) {
-                success(task, responseObject);
-            }
-        }
-    }];
+    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"POST" URLString:URLString parameters:parameters success:success failure:failure];
 
-    [task resume];
+    [dataTask resume];
 
-    return task;
+    return dataTask;
 }
 
 - (NSURLSessionDataTask *)POST:(NSString *)URLString
@@ -182,7 +150,20 @@ - (NSURLSessionDataTask *)POST:(NSString *)URLString
                        success:(void (^)(NSURLSessionDataTask *task, id responseObject))success
                        failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure
 {
-    NSMutableURLRequest *request = [self.requestSerializer multipartFormRequestWithMethod:@"POST" URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters constructingBodyWithBlock:block error:nil];
+    NSError *serializationError = nil;
+    NSMutableURLRequest *request = [self.requestSerializer multipartFormRequestWithMethod:@"POST" URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters constructingBodyWithBlock:block error:&serializationError];
+    if (serializationError) {
+        if (failure) {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wgnu"
+            dispatch_async(self.completionQueue ?: dispatch_get_main_queue(), ^{
+                failure(nil, serializationError);
+            });
+#pragma clang diagnostic pop
+        }
+
+        return nil;
+    }
 
     __block NSURLSessionDataTask *task = [self uploadTaskWithStreamedRequest:request progress:nil completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *error) {
         if (error) {
@@ -206,23 +187,11 @@ - (NSURLSessionDataTask *)PUT:(NSString *)URLString
                       success:(void (^)(NSURLSessionDataTask *task, id responseObject))success
                       failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure
 {
-    NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:@"PUT" URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:nil];
+    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"PUT" URLString:URLString parameters:parameters success:success failure:failure];
 
-    __block NSURLSessionDataTask *task = [self dataTaskWithRequest:request completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *error) {
-        if (error) {
-            if (failure) {
-                failure(task, error);
-            }
-        } else {
-            if (success) {
-                success(task, responseObject);
-            }
-        }
-    }];
+    [dataTask resume];
 
-    [task resume];
-
-    return task;
+    return dataTask;
 }
 
 - (NSURLSessionDataTask *)PATCH:(NSString *)URLString
@@ -230,23 +199,11 @@ - (NSURLSessionDataTask *)PATCH:(NSString *)URLString
                         success:(void (^)(NSURLSessionDataTask *task, id responseObject))success
                         failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure
 {
-    NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:@"PATCH" URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:nil];
-
-    __block NSURLSessionDataTask *task = [self dataTaskWithRequest:request completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *error) {
-        if (error) {
-            if (failure) {
-                failure(task, error);
-            }
-        } else {
-            if (success) {
-                success(task, responseObject);
-            }
-        }
-    }];
+    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"PATCH" URLString:URLString parameters:parameters success:success failure:failure];
 
-    [task resume];
+    [dataTask resume];
 
-    return task;
+    return dataTask;
 }
 
 - (NSURLSessionDataTask *)DELETE:(NSString *)URLString
@@ -254,23 +211,48 @@ - (NSURLSessionDataTask *)DELETE:(NSString *)URLString
                          success:(void (^)(NSURLSessionDataTask *task, id responseObject))success
                          failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure
 {
-    NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:@"DELETE" URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:nil];
+    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"DELETE" URLString:URLString parameters:parameters success:success failure:failure];
+
+    [dataTask resume];
+
+    return dataTask;
+}
+
+- (NSURLSessionDataTask *)dataTaskWithHTTPMethod:(NSString *)method
+                                       URLString:(NSString *)URLString
+                                      parameters:(id)parameters
+                                         success:(void (^)(NSURLSessionDataTask *, id))success
+                                         failure:(void (^)(NSURLSessionDataTask *, NSError *))failure
+{
+    NSError *serializationError = nil;
+    NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:method URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:&serializationError];
+    if (serializationError) {
+        if (failure) {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wgnu"
+            dispatch_async(self.completionQueue ?: dispatch_get_main_queue(), ^{
+                failure(nil, serializationError);
+            });
+#pragma clang diagnostic pop
+        }
+
+        return nil;
+    }
 
-    __block NSURLSessionDataTask *task = [self dataTaskWithRequest:request completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *error) {
+    __block NSURLSessionDataTask *dataTask = nil;
+    dataTask = [self dataTaskWithRequest:request completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *error) {
         if (error) {
             if (failure) {
-                failure(task, error);
+                failure(dataTask, error);
             }
         } else {
             if (success) {
-                success(task, responseObject);
+                success(dataTask, responseObject);
             }
         }
     }];
 
-    [task resume];
-
-    return task;
+    return dataTask;
 }
 
 #pragma mark - NSObject
@@ -279,7 +261,7 @@ - (NSString *)description {
     return [NSString stringWithFormat:@"<%@: %p, baseURL: %@, session: %@, operationQueue: %@>", NSStringFromClass([self class]), self, [self.baseURL absoluteString], self.session, self.operationQueue];
 }
 
-#pragma mark - NSecureCoding
+#pragma mark - NSSecureCoding
 
 + (BOOL)supportsSecureCoding {
     return YES;
@@ -291,7 +273,7 @@ - (id)initWithCoder:(NSCoder *)decoder {
     if (!configuration) {
         NSString *configurationIdentifier = [decoder decodeObjectOfClass:[NSString class] forKey:@"identifier"];
         if (configurationIdentifier) {
-#if (defined(__IPHONE_OS_VERSION_MAX_ALLOWED) && __IPHONE_OS_VERSION_MAX_ALLOWED >= 80000) || (defined(__MAC_OS_X_VERSION_MAX_ALLOWED) && __MAC_OS_X_VERSION_MAX_ALLOWED >= 1100)
+#if (defined(__IPHONE_OS_VERSION_MIN_REQUIRED) && __IPHONE_OS_VERSION_MIN_REQUIRED >= 80000) || (defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && __MAC_OS_X_VERSION_MIN_REQUIRED >= 1100)
             configuration = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:configurationIdentifier];
 #else
             configuration = [NSURLSessionConfiguration backgroundSessionConfiguration:configurationIdentifier];
diff --git a/QiniuSDK/AFNetworking/AFNetworkReachabilityManager.h b/QiniuSDK/AFNetworking/AFNetworkReachabilityManager.h
index 6320783..5e610d8 100644
--- a/QiniuSDK/AFNetworking/AFNetworkReachabilityManager.h
+++ b/QiniuSDK/AFNetworking/AFNetworkReachabilityManager.h
@@ -23,12 +23,6 @@
 #import <Foundation/Foundation.h>
 #import <SystemConfiguration/SystemConfiguration.h>
 
-#import <netinet/in.h>
-#import <netinet6/in6.h>
-#import <arpa/inet.h>
-#import <ifaddrs.h>
-#import <netdb.h>
-
 typedef NS_ENUM(NSInteger, AFNetworkReachabilityStatus) {
     AFNetworkReachabilityStatusUnknown          = -1,
     AFNetworkReachabilityStatusNotReachable     = 0,
@@ -88,11 +82,11 @@ typedef NS_ENUM(NSInteger, AFNetworkReachabilityStatus) {
 /**
  Creates and returns a network reachability manager for the socket address.
 
- @param address The socket address used to evaluate network reachability.
+ @param address The socket address (`sockaddr_in`) used to evaluate network reachability.
 
  @return An initialized network reachability manager, actively monitoring the specified socket address.
  */
-+ (instancetype)managerForAddress:(const struct sockaddr_in *)address;
++ (instancetype)managerForAddress:(const void *)address;
 
 /**
  Initializes an instance of a network reachability manager from the specified reachability object.
diff --git a/QiniuSDK/AFNetworking/AFNetworkReachabilityManager.m b/QiniuSDK/AFNetworking/AFNetworkReachabilityManager.m
index 71adaef..1da1482 100644
--- a/QiniuSDK/AFNetworking/AFNetworkReachabilityManager.m
+++ b/QiniuSDK/AFNetworking/AFNetworkReachabilityManager.m
@@ -22,6 +22,12 @@
 
 #import "AFNetworkReachabilityManager.h"
 
+#import <netinet/in.h>
+#import <netinet6/in6.h>
+#import <arpa/inet.h>
+#import <ifaddrs.h>
+#import <netdb.h>
+
 NSString * const AFNetworkingReachabilityDidChangeNotification = @"com.alamofire.networking.reachability.change";
 NSString * const AFNetworkingReachabilityNotificationStatusItem = @"AFNetworkingReachabilityNotificationStatusItem";
 
@@ -128,7 +134,7 @@ + (instancetype)managerForDomain:(NSString *)domain {
     return manager;
 }
 
-+ (instancetype)managerForAddress:(const struct sockaddr_in *)address {
++ (instancetype)managerForAddress:(const void *)address {
     SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithAddress(kCFAllocatorDefault, (const struct sockaddr *)address);
 
     AFNetworkReachabilityManager *manager = [[self alloc] initWithReachability:reachability];
diff --git a/QiniuSDK/AFNetworking/AFURLConnectionOperation.m b/QiniuSDK/AFNetworking/AFURLConnectionOperation.m
index e5e6839..d8b55e3 100644
--- a/QiniuSDK/AFNetworking/AFURLConnectionOperation.m
+++ b/QiniuSDK/AFNetworking/AFURLConnectionOperation.m
@@ -339,7 +339,6 @@ - (void)pause {
     }
     
     [self.lock lock];
-    
     if ([self isExecuting]) {
         [self performSelector:@selector(operationDidPause) onThread:[[self class] networkRequestThread] withObject:nil waitUntilDone:NO modes:[self.runLoopModes allObjects]];
         
@@ -350,7 +349,6 @@ - (void)pause {
     }
     
     self.state = AFOperationPausedState;
-    
     [self.lock unlock];
 }
 
@@ -466,6 +464,7 @@ - (void)operationDidStart {
             [self.outputStream scheduleInRunLoop:runLoop forMode:runLoopMode];
         }
         
+        [self.outputStream open];
         [self.connection start];
     }
     [self.lock unlock];
@@ -642,8 +641,6 @@ - (void)connection:(NSURLConnection __unused *)connection
 didReceiveResponse:(NSURLResponse *)response
 {
     self.response = response;
-    
-    [self.outputStream open];
 }
 
 - (void)connection:(NSURLConnection __unused *)connection
@@ -726,7 +723,7 @@ - (NSCachedURLResponse *)connection:(NSURLConnection *)connection
     }
 }
 
-#pragma mark - NSecureCoding
+#pragma mark - NSSecureCoding
 
 + (BOOL)supportsSecureCoding {
     return YES;
diff --git a/QiniuSDK/AFNetworking/AFURLRequestSerialization.h b/QiniuSDK/AFNetworking/AFURLRequestSerialization.h
index 161b551..17a4e49 100644
--- a/QiniuSDK/AFNetworking/AFURLRequestSerialization.h
+++ b/QiniuSDK/AFNetworking/AFURLRequestSerialization.h
@@ -135,6 +135,15 @@ typedef NS_ENUM(NSUInteger, AFHTTPRequestQueryStringSerializationStyle) {
 - (void)setValue:(NSString *)value
 forHTTPHeaderField:(NSString *)field;
 
+/**
+ Returns the value for the HTTP headers set in the request serializer.
+
+ @param field The HTTP header to retrieve the default value for
+ 
+ @return The value set as default for the specified header, or `nil`
+ */
+- (NSString *)valueForHTTPHeaderField:(NSString *)field;
+
 /**
  Sets the "Authorization" HTTP header set in request objects made by the HTTP client to a basic authentication value with Base64-encoded username and password. This overwrites any existing value for this header.
 
@@ -334,7 +343,7 @@ forHTTPHeaderField:(NSString *)field;
  Appends HTTP headers, followed by the encoded data and the multipart form boundary.
 
  @param headers The HTTP headers to be appended to the form data.
- @param body The data to be encoded and appended to the form data.
+ @param body The data to be encoded and appended to the form data. This parameter must not be `nil`.
  */
 - (void)appendPartWithHeaders:(NSDictionary *)headers
                          body:(NSData *)body;
diff --git a/QiniuSDK/AFNetworking/AFURLRequestSerialization.m b/QiniuSDK/AFNetworking/AFURLRequestSerialization.m
index 45df7a0..aea41d9 100644
--- a/QiniuSDK/AFNetworking/AFURLRequestSerialization.m
+++ b/QiniuSDK/AFNetworking/AFURLRequestSerialization.m
@@ -169,7 +169,20 @@ - (NSMutableURLRequest *)requestByFinalizingMultipartFormData;
 
 #pragma mark -
 
+static NSArray * AFHTTPRequestSerializerObservedKeyPaths() {
+    static NSArray *_AFHTTPRequestSerializerObservedKeyPaths = nil;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        _AFHTTPRequestSerializerObservedKeyPaths = @[NSStringFromSelector(@selector(allowsCellularAccess)), NSStringFromSelector(@selector(cachePolicy)), NSStringFromSelector(@selector(HTTPShouldHandleCookies)), NSStringFromSelector(@selector(HTTPShouldUsePipelining)), NSStringFromSelector(@selector(networkServiceType)), NSStringFromSelector(@selector(timeoutInterval))];
+    });
+
+    return _AFHTTPRequestSerializerObservedKeyPaths;
+}
+
+static void *AFHTTPRequestSerializerObserverContext = &AFHTTPRequestSerializerObserverContext;
+
 @interface AFHTTPRequestSerializer ()
+@property (readwrite, nonatomic, strong) NSMutableSet *mutableObservedChangedKeyPaths;
 @property (readwrite, nonatomic, strong) NSMutableDictionary *mutableHTTPRequestHeaders;
 @property (readwrite, nonatomic, assign) AFHTTPRequestQueryStringSerializationStyle queryStringSerializationStyle;
 @property (readwrite, nonatomic, copy) AFQueryStringSerializationBlock queryStringSerialization;
@@ -188,12 +201,6 @@ - (instancetype)init {
     }
 
     self.stringEncoding = NSUTF8StringEncoding;
-    self.allowsCellularAccess = YES;
-    self.cachePolicy = NSURLRequestUseProtocolCachePolicy;
-    self.HTTPShouldHandleCookies = YES;
-    self.HTTPShouldUsePipelining = NO;
-    self.networkServiceType = NSURLNetworkServiceTypeDefault;
-    self.timeoutInterval = 60;
 
     self.mutableHTTPRequestHeaders = [NSMutableDictionary dictionary];
 
@@ -229,20 +236,39 @@ - (instancetype)init {
     // HTTP Method Definitions; see http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html
     self.HTTPMethodsEncodingParametersInURI = [NSSet setWithObjects:@"GET", @"HEAD", @"DELETE", nil];
 
+    self.mutableObservedChangedKeyPaths = [NSMutableSet set];
+    for (NSString *keyPath in AFHTTPRequestSerializerObservedKeyPaths()) {
+        [self addObserver:self forKeyPath:keyPath options:NSKeyValueObservingOptionNew context:AFHTTPRequestSerializerObserverContext];
+    }
+
     return self;
 }
 
+- (void)dealloc {
+    for (NSString *keyPath in AFHTTPRequestSerializerObservedKeyPaths()) {
+        [self removeObserver:self forKeyPath:keyPath context:AFHTTPRequestSerializerObserverContext];
+    }
+}
+
 #pragma mark -
 
 - (NSDictionary *)HTTPRequestHeaders {
     return [NSDictionary dictionaryWithDictionary:self.mutableHTTPRequestHeaders];
 }
 
-- (void)setValue:(NSString *)value forHTTPHeaderField:(NSString *)field {
+- (void)setValue:(NSString *)value
+forHTTPHeaderField:(NSString *)field
+{
 	[self.mutableHTTPRequestHeaders setValue:value forKey:field];
 }
 
-- (void)setAuthorizationHeaderFieldWithUsername:(NSString *)username password:(NSString *)password {
+- (NSString *)valueForHTTPHeaderField:(NSString *)field {
+    return [self.mutableHTTPRequestHeaders valueForKey:field];
+}
+
+- (void)setAuthorizationHeaderFieldWithUsername:(NSString *)username
+                                       password:(NSString *)password
+{
 	NSString *basicAuthCredentials = [NSString stringWithFormat:@"%@:%@", username, password];
     [self setValue:[NSString stringWithFormat:@"Basic %@", AFBase64EncodedStringFromString(basicAuthCredentials)] forHTTPHeaderField:@"Authorization"];
 }
@@ -289,12 +315,12 @@ - (NSMutableURLRequest *)requestWithMethod:(NSString *)method
 
     NSMutableURLRequest *mutableRequest = [[NSMutableURLRequest alloc] initWithURL:url];
     mutableRequest.HTTPMethod = method;
-    mutableRequest.allowsCellularAccess = self.allowsCellularAccess;
-    mutableRequest.cachePolicy = self.cachePolicy;
-    mutableRequest.HTTPShouldHandleCookies = self.HTTPShouldHandleCookies;
-    mutableRequest.HTTPShouldUsePipelining = self.HTTPShouldUsePipelining;
-    mutableRequest.networkServiceType = self.networkServiceType;
-    mutableRequest.timeoutInterval = self.timeoutInterval;
+
+    for (NSString *keyPath in AFHTTPRequestSerializerObservedKeyPaths()) {
+        if ([self.mutableObservedChangedKeyPaths containsObject:keyPath]) {
+            [mutableRequest setValue:[self valueForKeyPath:keyPath] forKey:keyPath];
+        }
+    }
 
     mutableRequest = [[self requestBySerializingRequest:mutableRequest withParameters:parameters error:error] mutableCopy];
 
@@ -422,7 +448,16 @@ - (NSURLRequest *)requestBySerializingRequest:(NSURLRequest *)request
     if (parameters) {
         NSString *query = nil;
         if (self.queryStringSerialization) {
-            query = self.queryStringSerialization(request, parameters, error);
+            NSError *serializationError;
+            query = self.queryStringSerialization(request, parameters, &serializationError);
+
+            if (serializationError) {
+                if (error) {
+                    *error = serializationError;
+                }
+
+                return nil;
+            }
         } else {
             switch (self.queryStringSerializationStyle) {
                 case AFHTTPRequestQueryStringDefaultStyle:
@@ -435,8 +470,7 @@ - (NSURLRequest *)requestBySerializingRequest:(NSURLRequest *)request
             mutableRequest.URL = [NSURL URLWithString:[[mutableRequest.URL absoluteString] stringByAppendingFormat:mutableRequest.URL.query ? @"&%@" : @"?%@", query]];
         } else {
             if (![mutableRequest valueForHTTPHeaderField:@"Content-Type"]) {
-                NSString *charset = (__bridge NSString *)CFStringConvertEncodingToIANACharSetName(CFStringConvertNSStringEncodingToEncoding(self.stringEncoding));
-                [mutableRequest setValue:[NSString stringWithFormat:@"application/x-www-form-urlencoded; charset=%@", charset] forHTTPHeaderField:@"Content-Type"];
+                [mutableRequest setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
             }
             [mutableRequest setHTTPBody:[query dataUsingEncoding:self.stringEncoding]];
         }
@@ -445,7 +479,23 @@ - (NSURLRequest *)requestBySerializingRequest:(NSURLRequest *)request
     return mutableRequest;
 }
 
-#pragma mark - NSecureCoding
+#pragma mark - NSKeyValueObserving
+
+- (void)observeValueForKeyPath:(NSString *)keyPath
+                      ofObject:(__unused id)object
+                        change:(NSDictionary *)change
+                       context:(void *)context
+{
+    if (context == AFHTTPRequestSerializerObserverContext) {
+        if ([change[NSKeyValueChangeNewKey] isEqual:[NSNull null]]) {
+            [self.mutableObservedChangedKeyPaths removeObject:keyPath];
+        } else {
+            [self.mutableObservedChangedKeyPaths addObject:keyPath];
+        }
+    }
+}
+
+#pragma mark - NSSecureCoding
 
 + (BOOL)supportsSecureCoding {
     return YES;
@@ -650,7 +700,6 @@ - (void)appendPartWithInputStream:(NSInputStream *)inputStream
     [mutableHeaders setValue:[NSString stringWithFormat:@"form-data; name=\"%@\"; filename=\"%@\"", name, fileName] forKey:@"Content-Disposition"];
     [mutableHeaders setValue:mimeType forKey:@"Content-Type"];
 
-
     AFHTTPBodyPart *bodyPart = [[AFHTTPBodyPart alloc] init];
     bodyPart.stringEncoding = self.stringEncoding;
     bodyPart.headers = mutableHeaders;
@@ -747,6 +796,9 @@ @interface AFMultipartBodyStream () <NSCopying>
 @implementation AFMultipartBodyStream
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wimplicit-atomic-properties"
+#if (defined(__IPHONE_OS_VERSION_MAX_ALLOWED) && __IPHONE_OS_VERSION_MAX_ALLOWED >= 80000) || (defined(__MAC_OS_X_VERSION_MAX_ALLOWED) && __MAC_OS_X_VERSION_MAX_ALLOWED >= 1100)
+@synthesize delegate;
+#endif
 @synthesize streamStatus;
 @synthesize streamError;
 #pragma clang diagnostic pop
@@ -957,6 +1009,8 @@ - (NSInputStream *)inputStream {
             _inputStream = [NSInputStream inputStreamWithURL:self.body];
         } else if ([self.body isKindOfClass:[NSInputStream class]]) {
             _inputStream = self.body;
+        } else {
+            _inputStream = [NSInputStream inputStreamWithData:[NSData data]];
         }
     }
 
@@ -1124,7 +1178,7 @@ - (id)copyWithZone:(NSZone *)zone {
 @implementation AFJSONRequestSerializer
 
 + (instancetype)serializer {
-    return [self serializerWithWritingOptions:0];
+    return [self serializerWithWritingOptions:(NSJSONWritingOptions)0];
 }
 
 + (instancetype)serializerWithWritingOptions:(NSJSONWritingOptions)writingOptions
@@ -1167,7 +1221,7 @@ - (NSURLRequest *)requestBySerializingRequest:(NSURLRequest *)request
     return mutableRequest;
 }
 
-#pragma mark - NSecureCoding
+#pragma mark - NSSecureCoding
 
 - (id)initWithCoder:(NSCoder *)decoder {
     self = [super initWithCoder:decoder];
@@ -1247,7 +1301,7 @@ - (NSURLRequest *)requestBySerializingRequest:(NSURLRequest *)request
     return mutableRequest;
 }
 
-#pragma mark - NSecureCoding
+#pragma mark - NSSecureCoding
 
 - (id)initWithCoder:(NSCoder *)decoder {
     self = [super initWithCoder:decoder];
diff --git a/QiniuSDK/AFNetworking/AFURLResponseSerialization.h b/QiniuSDK/AFNetworking/AFURLResponseSerialization.h
index 36ed33e..ed1204c 100644
--- a/QiniuSDK/AFNetworking/AFURLResponseSerialization.h
+++ b/QiniuSDK/AFNetworking/AFURLResponseSerialization.h
@@ -285,10 +285,18 @@ extern NSString * const AFURLResponseSerializationErrorDomain;
  These keys may exist in the user info dictionary, in addition to those defined for NSError.
 
  - `NSString * const AFNetworkingOperationFailingURLResponseErrorKey`
+ - `NSString * const AFNetworkingOperationFailingURLResponseDataErrorKey`
 
  ### Constants
 
  `AFNetworkingOperationFailingURLResponseErrorKey`
  The corresponding value is an `NSURLResponse` containing the response of the operation associated with an error. This key is only present in the `AFURLResponseSerializationErrorDomain`.
+ 
+ `AFNetworkingOperationFailingURLResponseDataErrorKey`
+ The corresponding value is an `NSData` containing the original data of the operation associated with an error. This key is only present in the `AFURLResponseSerializationErrorDomain`.
  */
 extern NSString * const AFNetworkingOperationFailingURLResponseErrorKey;
+
+extern NSString * const AFNetworkingOperationFailingURLResponseDataErrorKey;
+
+
diff --git a/QiniuSDK/AFNetworking/AFURLResponseSerialization.m b/QiniuSDK/AFNetworking/AFURLResponseSerialization.m
index cc1e00b..7b042f7 100644
--- a/QiniuSDK/AFNetworking/AFURLResponseSerialization.m
+++ b/QiniuSDK/AFNetworking/AFURLResponseSerialization.m
@@ -30,6 +30,7 @@
 
 NSString * const AFURLResponseSerializationErrorDomain = @"com.alamofire.error.serialization.response";
 NSString * const AFNetworkingOperationFailingURLResponseErrorKey = @"com.alamofire.serialization.response.error.response";
+NSString * const AFNetworkingOperationFailingURLResponseDataErrorKey = @"com.alamofire.serialization.response.error.data";
 
 static NSError * AFErrorWithUnderlyingError(NSError *error, NSError *underlyingError) {
     if (!error) {
@@ -113,26 +114,33 @@ - (BOOL)validateResponse:(NSHTTPURLResponse *)response
     if (response && [response isKindOfClass:[NSHTTPURLResponse class]]) {
         if (self.acceptableContentTypes && ![self.acceptableContentTypes containsObject:[response MIMEType]]) {
             if ([data length] > 0) {
-                NSDictionary *userInfo = @{
-                                           NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: unacceptable content-type: %@", @"AFNetworking", nil), [response MIMEType]],
-                                           NSURLErrorFailingURLErrorKey:[response URL],
-                                           AFNetworkingOperationFailingURLResponseErrorKey: response
-                                           };
+                NSMutableDictionary *mutableUserInfo = [@{
+                                                          NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: unacceptable content-type: %@", @"AFNetworking", nil), [response MIMEType]],
+                                                          NSURLErrorFailingURLErrorKey:[response URL],
+                                                          AFNetworkingOperationFailingURLResponseErrorKey: response,
+                                                        } mutableCopy];
+                if (data) {
+                    mutableUserInfo[AFNetworkingOperationFailingURLResponseDataErrorKey] = data;
+                }
 
-                validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorCannotDecodeContentData userInfo:userInfo], validationError);
+                validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorCannotDecodeContentData userInfo:mutableUserInfo], validationError);
             }
 
             responseIsValid = NO;
         }
 
         if (self.acceptableStatusCodes && ![self.acceptableStatusCodes containsIndex:(NSUInteger)response.statusCode]) {
-            NSDictionary *userInfo = @{
-                                       NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: %@ (%ld)", @"AFNetworking", nil), [NSHTTPURLResponse localizedStringForStatusCode:response.statusCode], (long)response.statusCode],
-                                       NSURLErrorFailingURLErrorKey:[response URL],
-                                       AFNetworkingOperationFailingURLResponseErrorKey: response
-                                       };
+            NSMutableDictionary *mutableUserInfo = [@{
+                                               NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: %@ (%ld)", @"AFNetworking", nil), [NSHTTPURLResponse localizedStringForStatusCode:response.statusCode], (long)response.statusCode],
+                                               NSURLErrorFailingURLErrorKey:[response URL],
+                                               AFNetworkingOperationFailingURLResponseErrorKey: response,
+                                       } mutableCopy];
 
-            validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorBadServerResponse userInfo:userInfo], validationError);
+            if (data) {
+                mutableUserInfo[AFNetworkingOperationFailingURLResponseDataErrorKey] = data;
+            }
+
+            validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorBadServerResponse userInfo:mutableUserInfo], validationError);
 
             responseIsValid = NO;
         }
@@ -156,7 +164,7 @@ - (id)responseObjectForResponse:(NSURLResponse *)response
     return data;
 }
 
-#pragma mark - NSecureCoding
+#pragma mark - NSSecureCoding
 
 + (BOOL)supportsSecureCoding {
     return YES;
@@ -196,7 +204,7 @@ - (id)copyWithZone:(NSZone *)zone {
 @implementation AFJSONResponseSerializer
 
 + (instancetype)serializer {
-    return [self serializerWithReadingOptions:0];
+    return [self serializerWithReadingOptions:(NSJSONReadingOptions)0];
 }
 
 + (instancetype)serializerWithReadingOptions:(NSJSONReadingOptions)readingOptions {
@@ -256,8 +264,8 @@ - (id)responseObjectForResponse:(NSURLResponse *)response
                 }
             } else {
                 NSDictionary *userInfo = @{
-                                           NSLocalizedDescriptionKey: NSLocalizedStringFromTable(@"Data failed decoding as a UTF-8 string", nil, @"AFNetworking"),
-                                           NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Could not decode string: %@", nil, @"AFNetworking"), responseString]
+                                           NSLocalizedDescriptionKey: NSLocalizedStringFromTable(@"Data failed decoding as a UTF-8 string", @"AFNetworking", nil),
+                                           NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Could not decode string: %@", @"AFNetworking", nil), responseString]
                                            };
 
                 serializationError = [NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorCannotDecodeContentData userInfo:userInfo];
@@ -270,13 +278,13 @@ - (id)responseObjectForResponse:(NSURLResponse *)response
     }
     
     if (error) {
-        *error = AFErrorWithUnderlyingError(serializationError, *error);;
+        *error = AFErrorWithUnderlyingError(serializationError, *error);
     }
     
     return responseObject;
 }
 
-#pragma mark - NSecureCoding
+#pragma mark - NSSecureCoding
 
 - (id)initWithCoder:(NSCoder *)decoder {
     self = [super initWithCoder:decoder];
@@ -285,6 +293,7 @@ - (id)initWithCoder:(NSCoder *)decoder {
     }
 
     self.readingOptions = [[decoder decodeObjectOfClass:[NSNumber class] forKey:NSStringFromSelector(@selector(readingOptions))] unsignedIntegerValue];
+    self.removesKeysWithNullValues = [[decoder decodeObjectOfClass:[NSNumber class] forKey:NSStringFromSelector(@selector(removesKeysWithNullValues))] boolValue];
 
     return self;
 }
@@ -293,6 +302,7 @@ - (void)encodeWithCoder:(NSCoder *)coder {
     [super encodeWithCoder:coder];
 
     [coder encodeObject:@(self.readingOptions) forKey:NSStringFromSelector(@selector(readingOptions))];
+    [coder encodeObject:@(self.removesKeysWithNullValues) forKey:NSStringFromSelector(@selector(removesKeysWithNullValues))];
 }
 
 #pragma mark - NSCopying
@@ -300,6 +310,7 @@ - (void)encodeWithCoder:(NSCoder *)coder {
 - (id)copyWithZone:(NSZone *)zone {
     AFJSONResponseSerializer *serializer = [[[self class] allocWithZone:zone] init];
     serializer.readingOptions = self.readingOptions;
+    serializer.removesKeysWithNullValues = self.removesKeysWithNullValues;
 
     return serializer;
 }
@@ -394,7 +405,7 @@ - (id)responseObjectForResponse:(NSURLResponse *)response
     return document;
 }
 
-#pragma mark - NSecureCoding
+#pragma mark - NSSecureCoding
 
 - (id)initWithCoder:(NSCoder *)decoder {
     self = [super initWithCoder:decoder];
@@ -481,7 +492,7 @@ - (id)responseObjectForResponse:(NSURLResponse *)response
     return responseObject;
 }
 
-#pragma mark - NSecureCoding
+#pragma mark - NSSecureCoding
 
 - (id)initWithCoder:(NSCoder *)decoder {
     self = [super initWithCoder:decoder];
@@ -580,6 +591,8 @@ - (id)copyWithZone:(NSZone *)zone {
 
     if (colorSpaceModel == kCGColorSpaceModelRGB) {
         uint32_t alpha = (bitmapInfo & kCGBitmapAlphaInfoMask);
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wassign-enum"
         if (alpha == kCGImageAlphaNone) {
             bitmapInfo &= ~kCGBitmapAlphaInfoMask;
             bitmapInfo |= kCGImageAlphaNoneSkipFirst;
@@ -587,6 +600,7 @@ - (id)copyWithZone:(NSZone *)zone {
             bitmapInfo &= ~kCGBitmapAlphaInfoMask;
             bitmapInfo |= kCGImageAlphaPremultipliedFirst;
         }
+#pragma clang diagnostic pop
     }
 
     CGContextRef context = CGBitmapContextCreate(NULL, width, height, bitsPerComponent, bytesPerRow, colorSpace, bitmapInfo);
@@ -662,7 +676,7 @@ - (id)responseObjectForResponse:(NSURLResponse *)response
     return nil;
 }
 
-#pragma mark - NSecureCoding
+#pragma mark - NSSecureCoding
 
 - (id)initWithCoder:(NSCoder *)decoder {
     self = [super initWithCoder:decoder];
@@ -748,7 +762,7 @@ - (id)responseObjectForResponse:(NSURLResponse *)response
     return [super responseObjectForResponse:response data:data error:error];
 }
 
-#pragma mark - NSecureCoding
+#pragma mark - NSSecureCoding
 
 - (id)initWithCoder:(NSCoder *)decoder {
     self = [super initWithCoder:decoder];
diff --git a/QiniuSDK/AFNetworking/AFURLSessionManager.h b/QiniuSDK/AFNetworking/AFURLSessionManager.h
index 6432027..6939b7d 100644
--- a/QiniuSDK/AFNetworking/AFURLSessionManager.h
+++ b/QiniuSDK/AFNetworking/AFURLSessionManager.h
@@ -42,6 +42,7 @@
  
  - `URLSession:didBecomeInvalidWithError:`
  - `URLSession:didReceiveChallenge:completionHandler:`
+ - `URLSessionDidFinishEventsForBackgroundURLSession:`
 
  ### `NSURLSessionTaskDelegate`
  
@@ -56,7 +57,6 @@
  - `URLSession:dataTask:didBecomeDownloadTask:`
  - `URLSession:dataTask:didReceiveData:`
  - `URLSession:dataTask:willCacheResponse:completionHandler:`
- - `URLSessionDidFinishEventsForBackgroundURLSession:`
 
  ### `NSURLSessionDownloadDelegate`
 
diff --git a/QiniuSDK/AFNetworking/AFURLSessionManager.m b/QiniuSDK/AFNetworking/AFURLSessionManager.m
index 194cdfa..0775c4d 100644
--- a/QiniuSDK/AFNetworking/AFURLSessionManager.m
+++ b/QiniuSDK/AFNetworking/AFURLSessionManager.m
@@ -24,6 +24,16 @@
 
 #if (defined(__IPHONE_OS_VERSION_MAX_ALLOWED) && __IPHONE_OS_VERSION_MAX_ALLOWED >= 70000) || (defined(__MAC_OS_X_VERSION_MAX_ALLOWED) && __MAC_OS_X_VERSION_MAX_ALLOWED >= 1090)
 
+static dispatch_queue_t url_session_manager_creation_queue() {
+    static dispatch_queue_t af_url_session_manager_creation_queue;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        af_url_session_manager_creation_queue = dispatch_queue_create("com.alamofire.networking.session.manager.creation", DISPATCH_QUEUE_SERIAL);
+    });
+
+    return af_url_session_manager_creation_queue;
+}
+
 static dispatch_queue_t url_session_manager_processing_queue() {
     static dispatch_queue_t af_url_session_manager_processing_queue;
     static dispatch_once_t onceToken;
@@ -67,7 +77,7 @@ static dispatch_group_t url_session_manager_completion_group() {
 
 static NSString * const AFURLSessionManagerLockName = @"com.alamofire.networking.session.manager.lock";
 
-static NSUInteger const AFMaximumNumberOfToRecreateBackgroundSessionUploadTask = 3;
+static NSUInteger const AFMaximumNumberOfAttemptsToRecreateBackgroundSessionUploadTask = 3;
 
 static void * AFTaskStateChangedContext = &AFTaskStateChangedContext;
 
@@ -76,6 +86,7 @@ static dispatch_group_t url_session_manager_completion_group() {
 
 typedef NSURLRequest * (^AFURLSessionTaskWillPerformHTTPRedirectionBlock)(NSURLSession *session, NSURLSessionTask *task, NSURLResponse *response, NSURLRequest *request);
 typedef NSURLSessionAuthChallengeDisposition (^AFURLSessionTaskDidReceiveAuthenticationChallengeBlock)(NSURLSession *session, NSURLSessionTask *task, NSURLAuthenticationChallenge *challenge, NSURLCredential * __autoreleasing *credential);
+typedef void (^AFURLSessionDidFinishEventsForBackgroundURLSessionBlock)(NSURLSession *session);
 
 typedef NSInputStream * (^AFURLSessionTaskNeedNewBodyStreamBlock)(NSURLSession *session, NSURLSessionTask *task);
 typedef void (^AFURLSessionTaskDidSendBodyDataBlock)(NSURLSession *session, NSURLSessionTask *task, int64_t bytesSent, int64_t totalBytesSent, int64_t totalBytesExpectedToSend);
@@ -85,7 +96,6 @@ static dispatch_group_t url_session_manager_completion_group() {
 typedef void (^AFURLSessionDataTaskDidBecomeDownloadTaskBlock)(NSURLSession *session, NSURLSessionDataTask *dataTask, NSURLSessionDownloadTask *downloadTask);
 typedef void (^AFURLSessionDataTaskDidReceiveDataBlock)(NSURLSession *session, NSURLSessionDataTask *dataTask, NSData *data);
 typedef NSCachedURLResponse * (^AFURLSessionDataTaskWillCacheResponseBlock)(NSURLSession *session, NSURLSessionDataTask *dataTask, NSCachedURLResponse *proposedResponse);
-typedef void (^AFURLSessionDidFinishEventsForBackgroundURLSessionBlock)(NSURLSession *session);
 
 typedef NSURL * (^AFURLSessionDownloadTaskDidFinishDownloadingBlock)(NSURLSession *session, NSURLSessionDownloadTask *downloadTask, NSURL *location);
 typedef void (^AFURLSessionDownloadTaskDidWriteDataBlock)(NSURLSession *session, NSURLSessionDownloadTask *downloadTask, int64_t bytesWritten, int64_t totalBytesWritten, int64_t totalBytesExpectedToWrite);
@@ -253,6 +263,7 @@ @interface AFURLSessionManager ()
 @property (readwrite, nonatomic, strong) NSLock *lock;
 @property (readwrite, nonatomic, copy) AFURLSessionDidBecomeInvalidBlock sessionDidBecomeInvalid;
 @property (readwrite, nonatomic, copy) AFURLSessionDidReceiveAuthenticationChallengeBlock sessionDidReceiveAuthenticationChallenge;
+@property (readwrite, nonatomic, copy) AFURLSessionDidFinishEventsForBackgroundURLSessionBlock didFinishEventsForBackgroundURLSession;
 @property (readwrite, nonatomic, copy) AFURLSessionTaskWillPerformHTTPRedirectionBlock taskWillPerformHTTPRedirection;
 @property (readwrite, nonatomic, copy) AFURLSessionTaskDidReceiveAuthenticationChallengeBlock taskDidReceiveAuthenticationChallenge;
 @property (readwrite, nonatomic, copy) AFURLSessionTaskNeedNewBodyStreamBlock taskNeedNewBodyStream;
@@ -262,7 +273,6 @@ @interface AFURLSessionManager ()
 @property (readwrite, nonatomic, copy) AFURLSessionDataTaskDidBecomeDownloadTaskBlock dataTaskDidBecomeDownloadTask;
 @property (readwrite, nonatomic, copy) AFURLSessionDataTaskDidReceiveDataBlock dataTaskDidReceiveData;
 @property (readwrite, nonatomic, copy) AFURLSessionDataTaskWillCacheResponseBlock dataTaskWillCacheResponse;
-@property (readwrite, nonatomic, copy) AFURLSessionDidFinishEventsForBackgroundURLSessionBlock didFinishEventsForBackgroundURLSession;
 @property (readwrite, nonatomic, copy) AFURLSessionDownloadTaskDidFinishDownloadingBlock downloadTaskDidFinishDownloading;
 @property (readwrite, nonatomic, copy) AFURLSessionDownloadTaskDidWriteDataBlock downloadTaskDidWriteData;
 @property (readwrite, nonatomic, copy) AFURLSessionDownloadTaskDidResumeBlock downloadTaskDidResume;
@@ -284,20 +294,21 @@ - (instancetype)initWithSessionConfiguration:(NSURLSessionConfiguration *)config
         configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
     }
 
-    self.operationQueue = [[NSOperationQueue alloc] init];
-    self.operationQueue.maxConcurrentOperationCount = NSOperationQueueDefaultMaxConcurrentOperationCount;
+    self.sessionConfiguration = configuration;
 
-    self.responseSerializer = [AFJSONResponseSerializer serializer];
+    self.operationQueue = [[NSOperationQueue alloc] init];
+    self.operationQueue.maxConcurrentOperationCount = 1;
 
-    self.sessionConfiguration = configuration;
     self.session = [NSURLSession sessionWithConfiguration:self.sessionConfiguration delegate:self delegateQueue:self.operationQueue];
 
-    self.mutableTaskDelegatesKeyedByTaskIdentifier = [[NSMutableDictionary alloc] init];
+    self.responseSerializer = [AFJSONResponseSerializer serializer];
 
     self.securityPolicy = [AFSecurityPolicy defaultPolicy];
 
     self.reachabilityManager = [AFNetworkReachabilityManager sharedManager];
 
+    self.mutableTaskDelegatesKeyedByTaskIdentifier = [[NSMutableDictionary alloc] init];
+
     self.lock = [[NSLock alloc] init];
     self.lock.name = AFURLSessionManagerLockName;
     
@@ -337,8 +348,8 @@ - (void)setDelegate:(AFURLSessionManagerTaskDelegate *)delegate
     NSParameterAssert(task);
     NSParameterAssert(delegate);
 
+    [task addObserver:self forKeyPath:NSStringFromSelector(@selector(state)) options:(NSKeyValueObservingOptions)(NSKeyValueObservingOptionOld |NSKeyValueObservingOptionNew) context:AFTaskStateChangedContext];
     [self.lock lock];
-    [task addObserver:self forKeyPath:NSStringFromSelector(@selector(state)) options:NSKeyValueObservingOptionOld |NSKeyValueObservingOptionNew context:AFTaskStateChangedContext];
     self.mutableTaskDelegatesKeyedByTaskIdentifier[@(task.taskIdentifier)] = delegate;
     [self.lock unlock];
 }
@@ -393,13 +404,11 @@ - (void)addDelegateForDownloadTask:(NSURLSessionDownloadTask *)downloadTask
     delegate.manager = self;
     delegate.completionHandler = completionHandler;
 
-    delegate.downloadTaskDidFinishDownloading = ^NSURL * (NSURLSession * __unused session, NSURLSessionDownloadTask *task, NSURL *location) {
-        if (destination) {
+    if (destination) {
+        delegate.downloadTaskDidFinishDownloading = ^NSURL * (NSURLSession * __unused session, NSURLSessionDownloadTask *task, NSURL *location) {
             return destination(location, task.response);
-        }
-
-        return location;
-    };
+        };
+    }
 
     if (progress) {
         *progress = delegate.progress;
@@ -411,8 +420,8 @@ - (void)addDelegateForDownloadTask:(NSURLSessionDownloadTask *)downloadTask
 - (void)removeDelegateForTask:(NSURLSessionTask *)task {
     NSParameterAssert(task);
 
-    [self.lock lock];
     [task removeObserver:self forKeyPath:NSStringFromSelector(@selector(state)) context:AFTaskStateChangedContext];
+    [self.lock lock];
     [self.mutableTaskDelegatesKeyedByTaskIdentifier removeObjectForKey:@(task.taskIdentifier)];
     [self.lock unlock];
 }
@@ -466,11 +475,13 @@ - (NSArray *)downloadTasks {
 #pragma mark -
 
 - (void)invalidateSessionCancelingTasks:(BOOL)cancelPendingTasks {
-    if (cancelPendingTasks) {
-        [self.session invalidateAndCancel];
-    } else {
-        [self.session finishTasksAndInvalidate];
-    }
+    dispatch_async(dispatch_get_main_queue(), ^{
+        if (cancelPendingTasks) {
+            [self.session invalidateAndCancel];
+        } else {
+            [self.session finishTasksAndInvalidate];
+        }
+    });
 }
 
 #pragma mark -
@@ -486,7 +497,10 @@ - (void)setResponseSerializer:(id <AFURLResponseSerialization>)responseSerialize
 - (NSURLSessionDataTask *)dataTaskWithRequest:(NSURLRequest *)request
                             completionHandler:(void (^)(NSURLResponse *response, id responseObject, NSError *error))completionHandler
 {
-    NSURLSessionDataTask *dataTask = [self.session dataTaskWithRequest:request];
+    __block NSURLSessionDataTask *dataTask = nil;
+    dispatch_sync(url_session_manager_creation_queue(), ^{
+        dataTask = [self.session dataTaskWithRequest:request];
+    });
 
     [self addDelegateForDataTask:dataTask completionHandler:completionHandler];
 
@@ -500,9 +514,13 @@ - (NSURLSessionUploadTask *)uploadTaskWithRequest:(NSURLRequest *)request
                                          progress:(NSProgress * __autoreleasing *)progress
                                 completionHandler:(void (^)(NSURLResponse *response, id responseObject, NSError *error))completionHandler
 {
-    NSURLSessionUploadTask *uploadTask = [self.session uploadTaskWithRequest:request fromFile:fileURL];
+    __block NSURLSessionUploadTask *uploadTask = nil;
+    dispatch_sync(url_session_manager_creation_queue(), ^{
+        uploadTask = [self.session uploadTaskWithRequest:request fromFile:fileURL];
+    });
+
     if (!uploadTask && self.attemptsToRecreateUploadTasksForBackgroundSessions && self.session.configuration.identifier) {
-        for (NSUInteger attempts = 0; !uploadTask && attempts < AFMaximumNumberOfToRecreateBackgroundSessionUploadTask; attempts++) {
+        for (NSUInteger attempts = 0; !uploadTask && attempts < AFMaximumNumberOfAttemptsToRecreateBackgroundSessionUploadTask; attempts++) {
             uploadTask = [self.session uploadTaskWithRequest:request fromFile:fileURL];
         }
     }
@@ -517,7 +535,10 @@ - (NSURLSessionUploadTask *)uploadTaskWithRequest:(NSURLRequest *)request
                                          progress:(NSProgress * __autoreleasing *)progress
                                 completionHandler:(void (^)(NSURLResponse *response, id responseObject, NSError *error))completionHandler
 {
-    NSURLSessionUploadTask *uploadTask = [self.session uploadTaskWithRequest:request fromData:bodyData];
+    __block NSURLSessionUploadTask *uploadTask = nil;
+    dispatch_sync(url_session_manager_creation_queue(), ^{
+        uploadTask = [self.session uploadTaskWithRequest:request fromData:bodyData];
+    });
 
     [self addDelegateForUploadTask:uploadTask progress:progress completionHandler:completionHandler];
 
@@ -528,7 +549,10 @@ - (NSURLSessionUploadTask *)uploadTaskWithStreamedRequest:(NSURLRequest *)reques
                                                  progress:(NSProgress * __autoreleasing *)progress
                                         completionHandler:(void (^)(NSURLResponse *response, id responseObject, NSError *error))completionHandler
 {
-    NSURLSessionUploadTask *uploadTask = [self.session uploadTaskWithStreamedRequest:request];
+    __block NSURLSessionUploadTask *uploadTask = nil;
+    dispatch_sync(url_session_manager_creation_queue(), ^{
+        uploadTask = [self.session uploadTaskWithStreamedRequest:request];
+    });
 
     [self addDelegateForUploadTask:uploadTask progress:progress completionHandler:completionHandler];
 
@@ -542,7 +566,10 @@ - (NSURLSessionDownloadTask *)downloadTaskWithRequest:(NSURLRequest *)request
                                           destination:(NSURL * (^)(NSURL *targetPath, NSURLResponse *response))destination
                                     completionHandler:(void (^)(NSURLResponse *response, NSURL *filePath, NSError *error))completionHandler
 {
-    NSURLSessionDownloadTask *downloadTask = [self.session downloadTaskWithRequest:request];
+    __block NSURLSessionDownloadTask *downloadTask = nil;
+    dispatch_sync(url_session_manager_creation_queue(), ^{
+        downloadTask = [self.session downloadTaskWithRequest:request];
+    });
 
     [self addDelegateForDownloadTask:downloadTask progress:progress destination:destination completionHandler:completionHandler];
 
@@ -554,7 +581,10 @@ - (NSURLSessionDownloadTask *)downloadTaskWithResumeData:(NSData *)resumeData
                                              destination:(NSURL * (^)(NSURL *targetPath, NSURLResponse *response))destination
                                        completionHandler:(void (^)(NSURLResponse *response, NSURL *filePath, NSError *error))completionHandler
 {
-    NSURLSessionDownloadTask *downloadTask = [self.session downloadTaskWithResumeData:resumeData];
+    __block NSURLSessionDownloadTask *downloadTask = nil;
+    dispatch_sync(url_session_manager_creation_queue(), ^{
+        downloadTask = [self.session downloadTaskWithResumeData:resumeData];
+    });
 
     [self addDelegateForDownloadTask:downloadTask progress:progress destination:destination completionHandler:completionHandler];
 
@@ -581,6 +611,10 @@ - (void)setSessionDidReceiveAuthenticationChallengeBlock:(NSURLSessionAuthChalle
     self.sessionDidReceiveAuthenticationChallenge = block;
 }
 
+- (void)setDidFinishEventsForBackgroundURLSessionBlock:(void (^)(NSURLSession *session))block {
+    self.didFinishEventsForBackgroundURLSession = block;
+}
+
 #pragma mark -
 
 - (void)setTaskNeedNewBodyStreamBlock:(NSInputStream * (^)(NSURLSession *session, NSURLSessionTask *task))block {
@@ -621,10 +655,6 @@ - (void)setDataTaskWillCacheResponseBlock:(NSCachedURLResponse * (^)(NSURLSessio
     self.dataTaskWillCacheResponse = block;
 }
 
-- (void)setDidFinishEventsForBackgroundURLSessionBlock:(void (^)(NSURLSession *session))block {
-    self.didFinishEventsForBackgroundURLSession = block;
-}
-
 #pragma mark -
 
 - (void)setDownloadTaskDidFinishDownloadingBlock:(NSURL * (^)(NSURLSession *session, NSURLSessionDownloadTask *downloadTask, NSURL *location))block {
@@ -936,6 +966,7 @@ - (void)URLSession:(NSURLSession *)session
             if (error) {
                 [[NSNotificationCenter defaultCenter] postNotificationName:AFURLSessionDownloadTaskDidFailToMoveFileNotification object:downloadTask userInfo:error.userInfo];
             }
+
             return;
         }
     }
@@ -973,7 +1004,7 @@ - (void)URLSession:(NSURLSession *)session
     }
 }
 
-#pragma mark - NSecureCoding
+#pragma mark - NSSecureCoding
 
 + (BOOL)supportsSecureCoding {
     return YES;
diff --git a/README.md b/README.md
index 461436f..93a5a02 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,8 @@
 
 [![Qiniu Logo](http://qiniu-brand.qiniudn.com/5/logo-white-195x105.png)](http://www.qiniu.com/)
 
+## 新版SDK
+6.X版本基本不再更新, 建议使用新版本SDK，https://github.com/qiniu/objc-sdk
 
 ## 下载