what should I prepare in order to apply for a China visa?

Generally speaking, you need to submit your passport which should be valid for at least six months and has at least two blank pages, a photocopy of the passport, a filled-out application form attached with your recently-taken color bare-headed photo, and an invitation letter from a relevant entity in China.

Thanks so much for your respond. One more question , Where can I find the application form?

You can find it on the website of the embassy or the website of CVASC.