What are documents need for china visa?

I am Aman ullah.i have finished secondary exam.i got a offer letter in Riga int. School of eco. & business administration in Latvia.but there is no latvian embassy in our country.now i am go to china to one month visit for face to embassy of latvia in china in my latvian student visa.but i have no chineese invitation letter.so please tell me some information about to go china in visit visa with me?
Your truly Aman ullah.