diff --git a/Assets/YooAsset/Runtime/ResourceManager/Handle/SceneHandle.cs b/Assets/YooAsset/Runtime/ResourceManager/Handle/SceneHandle.cs
index b26914f..7b093ac 100644
--- a/Assets/YooAsset/Runtime/ResourceManager/Handle/SceneHandle.cs
+++ b/Assets/YooAsset/Runtime/ResourceManager/Handle/SceneHandle.cs
@@ -23,7 +23,7 @@ namespace YooAsset
             add
             {
                 if (IsValidWithWarning == false)
-                    throw new System.Exception($"{nameof(SceneHandle)} is invalid");
+                    throw new System.Exception($"{nameof(SceneHandle)} is invalid !");
                 if (Provider.IsDone)
                     value.Invoke(this);
                 else
@@ -32,7 +32,7 @@ namespace YooAsset
             remove
             {
                 if (IsValidWithWarning == false)
-                    throw new System.Exception($"{nameof(SceneHandle)} is invalid");
+                    throw new System.Exception($"{nameof(SceneHandle)} is invalid !");
                 _callback -= value;
             }
         }
@@ -168,13 +168,12 @@ namespace YooAsset
             }
 
             // 卸载子场景
+            // 注意：如果场景正在加载过程，必须等待加载完成后才可以卸载该场景。
             {
                 var operation = new UnloadSceneOperation(Provider);
                 OperationSystem.StartOperation(packageName, operation);
                 return operation;
             }
         }
-
-
     }
 }
\ No newline at end of file
diff --git a/Assets/YooAsset/Runtime/ResourceManager/Operation/UnloadSceneOperation.cs b/Assets/YooAsset/Runtime/ResourceManager/Operation/UnloadSceneOperation.cs
index c367bf5..a815cf2 100644
--- a/Assets/YooAsset/Runtime/ResourceManager/Operation/UnloadSceneOperation.cs
+++ b/Assets/YooAsset/Runtime/ResourceManager/Operation/UnloadSceneOperation.cs
@@ -14,14 +14,13 @@ namespace YooAsset
             CheckError,
             PrepareDone,
             UnLoadScene,
-            Checking,
             Done,
         }
 
         private ESteps _steps = ESteps.None;
         private readonly string _error;
         private readonly ProviderOperation _provider;
-        private AsyncOperation _asyncOp;
+        private AsyncOperation _asyncOp = null;
 
         internal UnloadSceneOperation(string error)
         {
@@ -96,16 +95,16 @@ namespace YooAsset
 
             if (_steps == ESteps.UnLoadScene)
             {
-                _asyncOp = SceneManager.UnloadSceneAsync(_provider.SceneObject);
-                _provider.ResourceMgr.UnloadSubScene(_provider.SceneName);
-                _steps = ESteps.Checking;
-            }
+                if (_asyncOp == null)
+                {
+                    _asyncOp = SceneManager.UnloadSceneAsync(_provider.SceneObject);
+                    _provider.ResourceMgr.UnloadSubScene(_provider.SceneName);
+                }
 
-            if (_steps == ESteps.Checking)
-            {
                 Progress = _asyncOp.progress;
                 if (_asyncOp.isDone == false)
                     return;
+
                 _provider.ResourceMgr.TryUnloadUnusedAsset(_provider.MainAssetInfo);
                 _steps = ESteps.Done;
                 Status = EOperationStatus.Succeed;
diff --git a/Assets/YooAsset/Runtime/ResourcePackage/Operation/DownloaderOperation.cs b/Assets/YooAsset/Runtime/ResourcePackage/Operation/DownloaderOperation.cs
index a2cee5f..f713f1e 100644
--- a/Assets/YooAsset/Runtime/ResourcePackage/Operation/DownloaderOperation.cs
+++ b/Assets/YooAsset/Runtime/ResourcePackage/Operation/DownloaderOperation.cs
@@ -130,7 +130,7 @@ namespace YooAsset
                 long downloadBytes = _cachedDownloadBytes;
                 foreach (var downloader in _downloaders)
                 {
-                    downloadBytes += (long)downloader.DownloadedBytes;
+                    downloadBytes += downloader.DownloadedBytes;
                     if (downloader.IsDone == false)
                         continue;
 
@@ -145,7 +145,7 @@ namespace YooAsset
                     // 下载成功
                     _removeList.Add(downloader);
                     _cachedDownloadCount++;
-                    _cachedDownloadBytes += (long)downloader.DownloadedBytes;
+                    _cachedDownloadBytes += downloader.DownloadedBytes;
                 }
 
                 // 移除已经完成的下载器（无论成功或失败）