Derivative polypeptide derived from a grass carp interferon and an application of the derivative polypeptide. An amino acid sequence of the derivative polypeptide is as shown in SEQ ID NO:1； the interferon-derived polypeptide has a high-efficiency antibacterial effect and can take effect against drug-resistant Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus agalactiae, Vibrio fluvialis or Aeromonas hydrophila. The interferon-derived polypeptide is less toxic to eukaryotes and can effectively reduce the mortality of mice in a mouse disease model caused by pathological bacteria. The interferon-derived polypeptide which is small in molecular weight is easily synthesized and has a good application value.
