diff --git a/KS3Sample/KS3Sample.cs b/KS3Sample/KS3Sample.cs
index dd8b03c549d33a84e4cd2e3c380f594d5e45e9e9..17be8ccd5b24cfec5b6a9f4017b3ecd07d00e256 100644
--- a/KS3Sample/KS3Sample.cs
+++ b/KS3Sample/KS3Sample.cs
@@ -519,7 +519,7 @@ namespace KS3Sample
             InitiateMultipartUploadResult result=multipartUp();
             FileInfo file = new FileInfo(path);
             int part = 5 * 1024 * 1024;
-            int numBytesToRead = (int)file.Length;
+            long numBytesToRead = file.Length;
             int i = 0;
             XElement root = new XElement("CompleteMultipartUpload");//初始化一个xml，以备分块上传完成后调用complete方法提交本次上传的文件以通知服务端合并分块
             //开始读取文件
diff --git a/readme.md b/readme.md
index 38f1311be2d82c087321e68e8223d3bbec5ceee8..f92d995f428c349f8173ee5c9ab796344e609f44 100644
--- a/readme.md
+++ b/readme.md
@@ -394,7 +394,7 @@
             InitiateMultipartUploadResult result=multipartUp();
             FileInfo file = new FileInfo(path);
             int part = 5 * 1024 * 1024;
-            int numBytesToRead = (int)file.Length;
+            long numBytesToRead = file.Length;
             int i = 0;
             XElement root = new XElement("CompleteMultipartUpload");//初始化一个xml，以备分块上传完成后调用complete方法提交本次上传的文件以通知服务端合并分块
             //开始读取文件
@@ -454,7 +454,7 @@
             InitiateMultipartUploadResult result = multipartUp();
             FileInfo file = new FileInfo(path);
             int part = 5 * 1024 * 1024;
-            int numBytesToRead = (int)file.Length;
+            long numBytesToRead = file.Length;
             int i = 0;
             XElement root = new XElement("CompleteMultipartUpload");//初始化一个xml，以备分块上传完成后调用complete方法提交本次上传的文件以通知服务端合并分块
             //开始读取文件