diff --git a/qcloud_cos/cos_client.py b/qcloud_cos/cos_client.py
index 08e67167..f651a107 100644
--- a/qcloud_cos/cos_client.py
+++ b/qcloud_cos/cos_client.py
@@ -2958,7 +2958,7 @@ def download_file(self, Bucket, Key, DestFilePath, PartSize=20, MAZThread=5, Ena
                      max_thread: {4}".format(Bucket, Key, DestFilePath, PartSize, MAZThread))
 
         object_info = self.head_object(Bucket, Key)
-        file_size = object_info['Content-Length']
+        file_size = int(object_info['Content-Length'])
         if file_size <= 1024*1024*20:
             response = self.get_object(Bucket, Key, **Kwargs)
             response['Body'].get_stream_to_file(DestFilePath)
diff --git a/qcloud_cos/resumable_downloader.py b/qcloud_cos/resumable_downloader.py
index 01d14090..61e9d2d4 100644
--- a/qcloud_cos/resumable_downloader.py
+++ b/qcloud_cos/resumable_downloader.py
@@ -73,8 +73,8 @@ def start(self):
         logger.debug('download success, bucket: {0}, key: {1}'.format(self.__bucket, self.__key))
 
     def __get_record_filename(self, bucket, key, dest_file_path):
-        dest_file_path_md5 = hashlib.md5(dest_file_path).hexdigest()
-        key_md5 = hashlib.md5(key).hexdigest()
+        dest_file_path_md5 = hashlib.md5(dest_file_path.encode("utf-8")).hexdigest()
+        key_md5 = hashlib.md5(key.encode("utf-8")).hexdigest()
         return '{0}_{1}.{2}'.format(bucket, key_md5, dest_file_path_md5)
 
     def __determine_part_size_internal(self, file_size, part_size):
@@ -90,7 +90,7 @@ def __determine_part_size_internal(self, file_size, part_size):
     def __splite_to_parts(self):
         parts = []
         file_size = int(self.__object_info['Content-Length'])
-        num_parts = (file_size + self.__part_size - 1) / self.__part_size
+        num_parts = int((file_size + self.__part_size - 1) / self.__part_size)
         for i in range(num_parts):
             start = i * self.__part_size
             if i == num_parts - 1: