Hi my son 17 years old is travelling alone to China to visit his Sister, may I know the requirments?

If he will go there for a short time, he can just apply for a tourist L type. He needs to provide those documents including your passport and copy of its data page, the application form, a recently-taken bareheaded color photo, an invitation letter from his sister, and a consent letter from his parents and copies of their passports as well as proof of financial support.