diff --git a/utils/downloader.py b/utils/downloader.py
index ee2bc67..e2d8e5f 100644
--- a/utils/downloader.py
+++ b/utils/downloader.py
@@ -68,7 +68,7 @@ def download_image(image_url, dst_dir, file_name, timeout=20, proxy_type=None, p
             print("## Fail:  {}  {}".format(image_url, e.args))
 
 
-def download_images(image_urls, dst_dir,timeout=20, proxy_type=None, proxy=None,files_name=None):
+def download_images(image_urls, dst_dir,timeout=20,concurrency=5, proxy_type=None, proxy=None,files_name=None):
     """
     Download image according to given urls and automatically rename them in order.
     :param timeout:
@@ -80,7 +80,6 @@ def download_images(image_urls, dst_dir,timeout=20, proxy_type=None, proxy=None,
     :param concurrency: number of requests process simultaneously
     :return: none
     """
-    concurrency = len(image_urls)
     with concurrent.futures.ThreadPoolExecutor(max_workers=concurrency) as executor:
         future_list = list()
         count = 0 
@@ -91,6 +90,7 @@ def download_images(image_urls, dst_dir,timeout=20, proxy_type=None, proxy=None,
             future_list.append(executor.submit(
                 download_image, image_url, dst_dir, file_name, timeout, proxy_type, proxy))
             count += 1
+        time.sleep(0.3)
         concurrent.futures.wait(future_list, timeout)
 
 def download_comic_icon():