diff --git a/thirdpart/captcha/conf/settings.py b/thirdpart/captcha/conf/settings.py
index e344bd9107..a57684b1f0 100644
--- a/thirdpart/captcha/conf/settings.py
+++ b/thirdpart/captcha/conf/settings.py
@@ -1,6 +1,7 @@
 import os
 from django.conf import settings
 
+CAPTCHA_IMAGE_SIZE = getattr(settings, 'CAPTCHA_IMAGE_SIZE', (90,42))
 CAPTCHA_FONT_PATH = getattr(settings, 'CAPTCHA_FONT_PATH', os.path.normpath(os.path.join(os.path.dirname(__file__), '..', 'fonts/Vera.ttf')))
 CAPTCHA_FONT_SIZE = getattr(settings, 'CAPTCHA_FONT_SIZE', 22)
 CAPTCHA_LETTER_ROTATION = getattr(settings, 'CAPTCHA_LETTER_ROTATION', (-35, 35))
diff --git a/thirdpart/captcha/views.py b/thirdpart/captcha/views.py
index 3b096f2d4a..bb9443293b 100644
--- a/thirdpart/captcha/views.py
+++ b/thirdpart/captcha/views.py
@@ -92,6 +92,7 @@ def captcha_image(request, key, scale=1):
     for f in settings.filter_functions():
         image = f(image)
 
+    image = image.resize(settings.CAPTCHA_IMAGE_SIZE, Image.ANTIALIAS)
     out = StringIO()
     image.save(out, "PNG")
     out.seek(0)