FileInfo info = new FileInfo(filePath); long fileSize = info.Length; Response.Clear(); Response.ContentType = "application/octet-stream"; Response.AddHeader("Content-Disposition", "attachement;filename=" + fileName); //指定檔案大小 Response.AddHeader("Content-Length", fileSize.ToString()); Response.WriteFile(filePath, 0, fileSize); Response.Flush(); Response.Close(); filepath為你剛次上傳的檔案路徑,fileName為檔名字,不懂可以再交流