ALAssetsLibrary *assetsLibrary=[[ALAssetsLibrary alloc]init];

            [assetsLibrary writeImageToSavedPhotosAlbum:[image CGImage] orientation:(ALAssetOrientation)[image imageOrientation] completionBlock:^(NSURL *assetURL, NSError *error) {

                if (error) {

                    NSLog(@"Save image fail：%@",error);

                }else{

                    NSLog(@"Save image succeed.");

                }

            }];

打印结果：

Save image fail：Error Domain=ALAssetsLibraryErrorDomain Code=-3311 "User denied access" UserInfo=0x14dc9660 {NSLocalizedDescription=User denied access, NSUnderlyingError=0x14db5200 "The operation couldn’t be completed. (ALAssetsLibraryErrorDomain error -3311.)", NSLocalizedFailureReason=The user has denied the application access to their media.}

原因是程序没用获取到用户权限，可以在"设置-隐私-照片\"选项中，允许应用访问你的手机相册。