This article approached comprehensively the conception，principle，prevention and cure of computer viruses，we analysed the mechanism and propagation principle of Pakistani Virus, and discribed ways to prevent and cure this virus，including the elimination way and the immunity way. In addition，this article illustrated that no thorough common way can be obtained to prevent and cure a11 the viruses，and a concrete analysis of concrete virus must be made. The most effective measure is the virus prevention.