Obtained by homologous recombination of replacing part coding region and common promotor region of cathepsin (v-cath) and chitinase (ChiA) genes with polyhedrin gene, the recombinant baculovirus BmNPVpolh+ CP－ChiA－GMCSF+, in which the v-cath and ChiA genes were inactivated, could express hGM-CSF gene and polyhedrin gene simultaneously. It was revealed that the inactivation of v-cath and ChiA genes had no significant effect on viral growth or polyhedron production in BmN cells, and the cells infected with the recombinant baculovirus BmNPVpolh+CP－ChiA－GMCSF+ survived 2 days more than those infected by BmNPV and BmNPV-hGMCSF, the expression level of foreign gene could be obviously improved. The B.mori larva infected with BmNPVpolh＋CP－ChiA－GMCSF＋ retained a healthy, normal white epidermis color, in contrast to the typical discoloration of the larval epidermis seen after death in wild-type BmNPV-infected larvae, whose cuticle becomes soft and easily punctured.