Any Foreign NGO wishing to establish a representative office or file for a temporary activity in China must compile a number of documents to be reviewed by public security authorities. That is the easy part.
Because China has not ratified the Hague Convention Abolishing the Requirement of Legalisation for Foreign Public Documents (the “Apostille Convention”), it does not recognize documents notarized in most places outside mainland China. This means that an NGO must go through a rather complicated multi-step process to notarize and authenticate its application materials before it can submit them for review, possibly including visits to far-flung local government offices, hundreds of dollars in processing fees, and in-depth discussions of the angle of a staple (really).
Gisa Dang and Siodhbhra Parkin provide a blow-by-blow account of how the process works here.