I am iraqi student in china

Basicly, you need to send them an invitation letter, better to be stamped by official office, such as your university or local foerign affairs. Together with copies of your passport, China student visa/residence permit. Other documents needed are their original passport and photocopy of the information page of passport, application form attached with photo, return tickets and hotel reservation. If necessary, they are required to provide financial support as a proof that they can cover their expenditure in China.