http://www.cnn.com/2014/09/11/world/asia/china-us-isis/

U.S . likely to get Beijing's 'quiet' support in bid to destroy ISIS, analysts say

"If these groups have cells in Xinjiang, if it can be confirmed that ISIS members were recruited from China, if we are already becoming a ground for recruitment for these people then China has a stake in keeping ISIS away from its borders," said Xie.
In response to a reporter's question on whether China would join U.S. efforts to combat terrorism, Hua Chunying, China's foreign ministry spokesperson, said that China hoped that "with joint efforts of the international community, the countries involved will soon restore stability and order, achieve reconciliation, peace and development."

"Abiding by the principles of mutual respect and equal cooperation, China is willing to enhance anti-terrorism communication and cooperation with the international community so as to safeguard international security and stability," she added.
We'll see how this plays out, I have little faith in China actually moving beyond words, but then even words supporting the effort is a positive movement.