Abstract: Objective To explore the expression level of antibacterial peptide genes at the different development stages of Musca domestica. Methods Total RNA was extracted from eggs, 1st instar larvae, 2nd instar larvae, 3rd instar larvae, pupae and adults of M. domestica. After the primers for antibacterial peptide （cecropin, defensin and attacin） genes and GAPDH were designed respectively according to the reported M. domestica gene sequences in GenBank, semi-quantitative RT-PCR was performed to detect expression level of these genes in the development stages of M. dome-stica using GAPDH as inner control. Results The antibacterial peptide genes were detected with bandｓ of 210 bp, 300 bp and 650 bp at all development stages of M. domestica. The expression level in the 3rd instar larvae and adults were higher, with a band value of cecropin, defensin and attacin in relation to GAPDH of 1.61, 1.99, 1.62 and 1.47, 1.92, 1.59, respectively; while it was lower at eggs, 1st instar larvae and pupae with a band value of cecropin, defensin and attacin 0.49, 0.49, 0.42 and 0.72, 0.49, 0.64 and 0.65, 0.39, 0.91, respectively. Conclusion The antibacterial peptide genes express at all development stages of M. domestica with an evidently different expression level．

Key words: Musca domestica, Antibacterial peptide, Gene expression, RT-PCR