How do I apply for a Permanent Visa to live in China?

At present I am living in Wuzhou, China, on a two year visa, which expires on July2014. How can I apply for a Permanent type, to live in China. We have(wife), our own appartment in Wuzhou, China. I am at present working voluntarily as an English teacher, to local Chinese.? I am a British Citizen, with a UK passport. My wife is Chinese.