The invention discloses an antibacterial peptide BV21. The amino acid sequence of the antibacterial peptide BV21 is described as SEQ ID NO:1. The antibacterial peptide BV21 has the advantages of small molecular weight, convenience for artificial synthesis, low cost, strong bactericidal effects and low cytotoxicity, etc. The application of the antibacterial peptide BV21 in feed for livestock and poultry can significantly improve the growth performance of the livestock and poultry, improve the intestinal health of the livestock and poultry, increase the daily gain of weaning piglets and reduce the feed weight ratio.