The study on the inheritance of Nuclear Polyhedrosis Virus(NPV) resistance in Bombyx mori that infected by peroral was carried out based on probit analysis method and curve analysis between density of NPV(logarithm) and the death ratio.It can be indicated from the results that the inheritance of NPV-resistance controlled by a major dominant gene together with many minor genes.The F_1 and F_2 progeny show patrolclinal tendency in NPV-resistance inheritance and F_1 shows heterosis.