A novel antimicrobial polypeptidc was isolated and charaeterized from loach,Misgurmis anguillieaudatus, The polypcptide, named MAPP, is a single-chain polypcptide with Mw about 9,800 Dalton and p1 about 4.78; the N-tag ofMAPP was CFGWN. MAPP showed good inhibition against various bacteria including Bacillus subtilis, Eseherichia coli and Staphylococcus aurens. MAPP could be used as a lead compound in antibiotics drug discovery.