The invention discloses a preparation method of an antioxidative peptide of a hairtail. The preparation method comprises the following steps of 1, adding water into hairtails, and mincing the hairtails into hairtail paste, 2, adding the hairtail paste into an enzymolysis tank, and adding endoprotease into the hairtail paste for hydrolysis, wherein the mass of the endoprotease is 0.2 to 0.9% of the mass of the hairtails, 3, carrying out centrifugation of a hydrolysate obtained by the step 2, and collecting a supernatant, 4, carrying out microfiltration of the supernatant, adding the micro-filtrated supernatant into the enzymolysis tank, and adding excision protease into the enzymolysis tank for hydrolysis, wherein the mass of the excision protease is 0.1 to 0.9% of the mass of the hairtails, 5, in the hydrolysis, pumping an enzymatic hydrolysate into an ultrafiltration membrane separator from the enzymolysis tank so that the enzymatic hydrolysate can be circulated at a flow of 0.1 to 0.5L/min, and 6, collecting an ultrafiltration membrane permeate, carrying out reduced pressure concentration until a volume of the ultrafiltration membrane permeate is 1/10 to 1/5 of the original volume, keeping a temperature of -18 to -20 DEG C for a night, and carrying out freeze drying at a temperature of -60 to -65 DEG C under the pressure of 0.005 to 0.0054 mbar to obtain the antioxidative peptide of hairtails. The antioxidative peptide of hairtails has strong antioxidation activity, a hydroxyl radical removal rate of 82.0%, a superoxide anion radical removal rate of 85.2% and a DPPH radical removal rate of 61.5%.