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 consists 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. Parasin I shows exceptionally potent antimicrobial activity against a broad spectrum of microorganisms, including Gram-positive and Gram-negative bacteria and fungi, without any hemolytic activity. Its synthetic derivatives also have potent activity. Therefore, parasin I and its derivatives can be used as wound healing agents, trauma curing agent, mouthwash, eyewash, etc.