The present invention discloses the use of low molecular polypeptide ZY4 in preparing drugs for acne, infection and cancer as well as cosmetics. It comprises 17 amino acid residues, with a molecular weight of 2374.0 Da, an isoelectric point of 10.74, and its amino acid sequence is as shown in SEQ ID:1. The low molecular polypeptide ZY4 in the invention is artificially synthesized, with the advantages of small molecular weight and convenient artificial synthesis. The experiments have showed that the polypeptide ZY4 has clear antibacterial effect and has significant therapeutic effect on acne. The polypeptides can inhibit the growth of tumor cells and kill tumor cells； and the low molecular polypeptide ZY4 can be used in the preparation of anti-infective, anti-tumor and anti-acne medicaments and cosmetics.
