Several strains of silkworm Bombyx mori were tested for the gene delivery feasibility of Autographa californica nucleopolyhedrovirus (AcNPV) in vivo. In contrast to the general belief that silkworms were non-permissive to AcNPV, we found that 3 of 7 tested strains were AcNPV permissive. To dispel the physiological influence of the ecdysteroid UDP-glucosyltransferase (EGT) on the silkworm, we modified the AcNPV bacmid by disruption of that gene. Expression pattern of EGFP in tissues of silkworm larvae after injection of EGT-null AcNPV vector carrying EGFP cassette was revealed by green fluorescence and Western blot analysis. Viral DNA was detected and semi-quantified in various kinds of tissues by dot blot assay. Active recombinant virus from larval hemolymph was detectable by TCID(50). Our results indicate that some strains of silkworm were permissive to AcNPV, which could serve as a novel gene deliver tool to silkworm in vivo.