I am not so much familiar with the adult scene (if there even is such a thing) in China. As far as I know, it is illegal to produce porn movies in China, but I am not sure if it is forbidden to run tube sites that embed videos, so you have to research it yourself. You should be able to register a domain, get a hosting and set up an adult site on it without any problem but you might get into the trouble once the authorities find out about it. The best thing is to run it from abroad where it is allowed.