diff --git a/utils/downloader.py b/utils/downloader.py
index 6d026ce..b40b778 100644
--- a/utils/downloader.py
+++ b/utils/downloader.py
@@ -80,7 +80,15 @@ def download_images(image_urls, dst_dir, file_prefix="img", concurrency=50, time
     :param concurrency: number of requests process simultaneously
     :return: none
     """
-    concurrency = len(image_urls) 
+    file_count = 0
+    count = 0
+    for image_url in image_urls:
+        file_name = filesName[count]
+        file_path = os.path.join(dst_dir, file_name)
+        if not os.path.exists(file_path):
+            file_count += 1
+        count += 1
+    concurrency = int(file_count)
     with concurrent.futures.ThreadPoolExecutor(max_workers=concurrency) as executor:
         future_list = list()
         count = 0