how can i apply S1 type in China if i am holding S2 type?

Hi, you can try to convert your current S2 type to an S1 type at the exit and entry administration of the local PSB within China. If it can be done, you don't need to leave China.
You need to provide passport, a passport-style photo, a completed application form, valid registration form of temporary residence, an invitation letter, copy of inviter's ID card or inviter's passport, residence permit and the copies, as well as your relationship certificate. And then go to the exit and entry administration of the local PSB to make the conversion.