diff --git a/Assets/YooAsset/Runtime/DownloadSystem/Downloader/DownloadHandlerFileRange.cs b/Assets/YooAsset/Runtime/DownloadSystem/Downloader/DownloadHandlerFileRange.cs
new file mode 100644
index 0000000..d8ee959
--- /dev/null
+++ b/Assets/YooAsset/Runtime/DownloadSystem/Downloader/DownloadHandlerFileRange.cs
@@ -0,0 +1,87 @@
+using System;
+using System.IO;
+using UnityEngine;
+using UnityEngine.Networking;
+
+namespace YooAsset
+{
+	/// <summary>
+	/// 支持Unity2018版本的断点续传下载器
+	/// </summary>
+	public class DownloadHandlerFileRange : DownloadHandlerScript
+	{
+		private string _fileSavePath;
+		private long _fileTotalSize;
+		private UnityWebRequest _webRequest;
+		private FileStream _fileStream;
+
+		private long _localFileSize = 0;
+		private long _curFileSize = 0;
+
+
+		public DownloadHandlerFileRange(string fileSavePath, long fileTotalSize, UnityWebRequest webRequest) : base(new byte[1024 * 1024])
+		{
+			_fileSavePath = fileSavePath;
+			_fileTotalSize = fileTotalSize;
+			_webRequest = webRequest;
+
+			if (File.Exists(fileSavePath))
+			{
+				FileInfo fileInfo = new FileInfo(fileSavePath);
+				_localFileSize = fileInfo.Length;
+			}
+
+			_fileStream = new FileStream(_fileSavePath, FileMode.Append, FileAccess.Write);
+			_curFileSize = _localFileSize;
+		}
+		protected override bool ReceiveData(byte[] data, int dataLength)
+		{
+			if (data == null || dataLength == 0 || _webRequest.responseCode >= 400)
+				return false;
+
+			if (_fileStream == null)
+				return false;
+
+			_fileStream.Write(data, 0, dataLength);
+			_curFileSize += dataLength;
+			return true;
+		}
+
+		/// <summary>
+		/// UnityWebRequest.downloadHandler.data
+		/// </summary>
+		protected override byte[] GetData()
+		{
+			return null;
+		}
+
+		/// <summary>
+		/// UnityWebRequest.downloadHandler.text
+		/// </summary>
+		protected override string GetText()
+		{
+			return null;
+		}
+
+		/// <summary>
+		/// UnityWebRequest.downloadProgress
+		/// </summary>
+		protected override float GetProgress()
+		{
+			return _fileTotalSize == 0 ? 0 : ((float)_curFileSize) / _fileTotalSize;
+		}
+
+		/// <summary>
+		/// 释放下载句柄
+		/// </summary>
+		public void Cleanup()
+		{
+			if (_fileStream != null)
+			{
+				_fileStream.Flush();
+				_fileStream.Dispose();
+				_fileStream = null;
+			}
+		}
+	}
+}
\ No newline at end of file
diff --git a/Assets/YooAsset/Runtime/DownloadSystem/Downloader/DownloadHandlerFileRange.cs.meta b/Assets/YooAsset/Runtime/DownloadSystem/Downloader/DownloadHandlerFileRange.cs.meta
new file mode 100644
index 0000000..ff557b1
--- /dev/null
+++ b/Assets/YooAsset/Runtime/DownloadSystem/Downloader/DownloadHandlerFileRange.cs.meta
@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: 94254ab8e4496214884c11a891c131c6
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 
diff --git a/Assets/YooAsset/Runtime/DownloadSystem/Downloader/FileDownloader.cs b/Assets/YooAsset/Runtime/DownloadSystem/Downloader/FileDownloader.cs
index c3c2d55..b8253cd 100644
--- a/Assets/YooAsset/Runtime/DownloadSystem/Downloader/FileDownloader.cs
+++ b/Assets/YooAsset/Runtime/DownloadSystem/Downloader/FileDownloader.cs
@@ -9,8 +9,9 @@ namespace YooAsset
 {
 	internal sealed class FileDownloader : DownloaderBase
 	{
-		private UnityWebRequest _webRequest;
-		private bool _breakResume;
+		private readonly bool _breakResume;
+		private UnityWebRequest _webRequest = null;
+		private DownloadHandlerFileRange _downloadHandle = null;
 
 		// 重置变量
 		private bool _isAbort = false;
@@ -40,7 +41,7 @@ namespace YooAsset
 				}
 				else
 				{
-					if(verifyResult == EVerifyResult.FileOverflow)
+					if (verifyResult == EVerifyResult.FileOverflow)
 					{
 						string cacheFilePath = _bundleInfo.Bundle.CachedFilePath;
 						if (File.Exists(cacheFilePath))
@@ -75,8 +76,15 @@ namespace YooAsset
 
 					_requestURL = GetRequestURL();
 					_webRequest = UnityWebRequest.Get(_requestURL);
-					DownloadHandlerFile handler = new DownloadHandlerFile(fileSavePath, true);
+
+#if UNITY_2019_4_OR_NEWER
+					var handler = new DownloadHandlerFile(fileSavePath, true);
 					handler.removeFileOnAbort = false;
+#else
+					var handler = new DownloadHandlerFileRange(fileSavePath, _bundleInfo.Bundle.FileSize, _webRequest);
+					_downloadHandle = handler;
+#endif
+
 					_webRequest.downloadHandler = handler;
 					_webRequest.disposeDownloadHandlerOnDispose = true;
 					if (fileLength > 0)
@@ -218,6 +226,12 @@ namespace YooAsset
 		}
 		private void DisposeWebRequest()
 		{
+			if(_downloadHandle != null)
+			{
+				_downloadHandle.Cleanup();
+				_downloadHandle = null;
+			}
+
 			if (_webRequest != null)
 			{
 				_webRequest.Dispose();