Disclosed is a novel antimicrobial peptide, named parasin I, which is isolated from catfish. Catfish produce a strong antimicrobial peptide in the epithelial mucosal layer upon epidermal injury to protect against the invasion of microorganisms. It is 2000.4 Da in molecular mass and consist of 19 amino acid residues, represented by Lys-Gly-Arg-Gly-Lys-Gln-Gly-Gly-Lys-Val-Arg-Ala-Lys-Ala-Lys-Thr-Arg-Ser-Ser (SEQ ID NO: 1) Parasin I shows exceptionally potent antimicrobial activity against a broad spectrum of micrroorganisms, including Gram-positive and Gram-negative bacteria and fungui, without any hemolytic activity. Its synthetic derivatives also have potent activity. Therefore, parasin I and its derivatives can be used as wound healing agent, trauma curing agent, mouthwash, eyewash, etc.