Three model silkworms, highly resistant strain, highly susceptible strain and their near isogenic line were established by hybridization and backcross. The resistance of silkworm (Bombyx mori L.) to BmNPV was studied at proteomic level using two-dimensional gel electrophoresis and MALDI TOF/TOF MS. Differential expression profiles of proteome in resistant strain, susceptible strain and near isogenic line were obtained, and 180, 190 and 187 of protein spots were shown, respectively. Among them, 80% were concentrated in pI 5~9. Twelve differential protein spots in total were obtained from 3 gels. Using MALDI TOF/TOF MS, five proteins, including aminoacylase, were identified from these spots. The exclusive expression of aminoacylase in highly resistant strain and near isogenic line and its absence in susceptible strain suggest that it might be a BmNPV-resistance related protein.