I am engaged with my fiance who is a Chinese in mainland, how do i get a visa with multiple entries?

The required documents and application of multiple entries are the same as the application for single-entry visa. After you get married, you should live in China for 5 years in a row and the annual stay is no less than 9 months. Also, you have stable and secured living status and place to live in PRC, and then you can apply for the permanent residence permit.