Effect on the bacterial cell surface characteristics and cell membrane of the antibacterial peptide of the larvae of housefly (Musca domestica) was studied by MATS, microelectrophoresis and measuring the hydrolysis of o-nitrophenyl-L-D-galactoside(ONPG) by the cell β-galactosidase. The results indicated that the antibacterial peptide of the housefly larvae could increase the negative charge of the cell surface, more potently to the G⁺ than the G^-, and could decrease the hydropobicity of the cell surface. The results also suggested that the antibacterial peptide could increase the permeability of the cell membrane, the regression equation of the time course of o-nitrophenol(ONP) was obtained, and the maximum velocity of ONPG hydrolysis(V_P) was calculated to be 3.86 pmol/min-6.92 pmol/min for various tested bacteria at 0 minute.It was suggested that the antibacterial peptide may act on the cell membrane through the “pore forming " mechanism.