Please I want to know which documents I need for S1 visa

Nano, you need to prepare your passport and copy of its data page, the application form, a passport-style photo, an invitation letter, copy of the inviter's passport and residence permit, relationship certificate and its copy.
You can only stay in China for 30 days with S1 type, so if you want to stay more than 180 days, you need to apply for a residence permit within 30 days after your entry at the exit and entry administration of the local PSB.