Can I know the procedure to apply visit visa for two people?

You need to submit the following requirements to China embassy in Sri Lanka to apply for the tourist visa:
1. applicants' valid passport, passport photos, visa application forms and travel information including the booking of airline ticket and itinerary in China. The visa officer will then process the visa for you, usually in 4 working days.

Thanks. We are planning to visit a friend in china if so do we need a letter from him?

Ayanthi, sorry to tell you that China embassy in Colombo doesn't issue individual tourist visa to Sri Lanka nationals. You have to join a tour (at least 5 members) to apply for a Group Tourist Visa to China.