AIDS is a kind of severe disease caused by human immunodeficiency virus(HIV). It has the characteristic of high death rate, high spreading speed and causing grave damage. HIV is divided into two types, HIV-1 and HIV-2, and AIDS is mainly caused by HIV-1. The mutation rate of HIV-1 is high and kinds of subtypes with different gene sequence occur during spreading. The study of molecular epidemiology of HIV-1, especially the subtype detection, plays important role in tracing infection origin, controlling epide...