A method of preparing an anti-oxidation polypeptide having an amino acid sequence of SEQ ID NO:1 includes enzymatic hydrolysis of black shark skins, which serve as the raw material, with alkali protease, separation, purification, freezing, and drying to obtain the anti-oxidation polypeptide. Enzymatic hydrolysis conditions include 7.0-9.0 pH value, 40-50° C. temperature, 4.0-6.0 h enzymatic hydrolysis time, 2.0-4.0% primer concentration, and 9.0-10.0 wt % of enzymes.