Here is a good way to do it. Use Wanyoutube.com.
Wantyoutube is easy to use. I'll do some introduction to it. Wantyoutube is so popular now that people like to use it for free.Besides downloading Tudou, Wantyoutube can watch Tudou directly even if you're not in the Mainland China.
Wantyoutube provides a special method to download Tudou: Just add a "want" in the URL. Then you can have Tudou videos in seconds.
(i. e: www.tudou.com/xxax change to www.wanttudou.com/xxax, and press ENTER)
Introduction for Wantyoutube:
Wantyoutube supports lots of sites you may like: 5min, Break, Current, Dailymotion, Facebook,Google Video, ku6, Megavideo, Megaporn, Metacafe, Myspace, Photobucket, Sina, Spike, Tudou, Veoh, Vimeo, Yahoo Videos, FC2, Yam, Youku, Youtube, Xuite, Xvideos, 56.com, etc...
Wantyoutube can directly download video formats like:
MP3, MP4, 3GP, WebM, FLV, HD Quality Movir, etc…
Go and try: http://www.wantyoutube.com/
