The first website I would try is http://www.scaashanghai.org/
What you are getting there is the Second Chance Animal Aid's Shaghai website. The good thing is that Second Chance Animal Aid has been around for over a decade, so there is less of a worry that it is some scam based website looking for dollars. The other good thing about the website is that not only is Second Chance Animal Aid looking for your donation, but also you can participate in the rescue and rehabilitation of animals. In the left hand navigation of the website there are links for donation, pet adoption, pet fostering, and even directions on how to turn in a rescued animal that you can't take care of.
A second website is https://www.animalsasia.org/us/
Animals Asia is an even older and more well established program than Second Chance Animal Aid. One significant difference though is that Animals Asia works in closer relationships with zoos and animal sanctuaries. The reason for that is because Animals Asia not only focuses on the cat, dog, pet industry and homeless animals, but also on rescuing bears in the region.
The third website is http://www.worldanimalprotection.org/
Not China specific, but World Animal Protection is a global entity and does some operations in China.
On website that I have found is a global website dedicated to helping homeless animals in China. (The link is posted below). China lacks many of the animal humane laws that other countries such as the United States have, and many countries all over the world are noticing this and working to help them as much as possible.