Abstract: Objective To identify the antibacterial peptide from the larvae of Mu scadomestica with tris-tricine sodium dodecyl sulfate polyacrylam idegel electrophoresis(SDS-PAGE)and pepitde finger printing method.Methods The antibac terial peptide was separated and purified form the secretion of Mu scadomesticala rvae.The molecular weight of the peptide was determined with tric-tricine SDS-PAGE;the an tibacterial piptide molecule was identified with peptide finger printing method.Results Two active compounds were isolated and named as secreting type an tibacterial peptideⅡ(AP-Ⅱ) and secreting type antibacterial peptideⅡ(AP-Ⅱ).The irmolecular weihgt are 14.157 kDa and 7.579 kDa by SDS-PAGE,respectively,and the accurate molecular weight of AP-1 is 14.264 kDa determined with mass spectrum technique.There is a homology between AP-1 and lysozyme of the aminoacid sequence.Fraction of sequence coverage is 20%.But they are different pioteins according to their different biochemical charac teristics.Conclusion The AP-1isolated from secretion of Musca donestica larvae has some homology and different biochemical charateristics withly sozyme.