In this study, the ability of removing superoxide anion,hydroxyl free radical and DPPH was taken as an index to study the antioxidant activities of three kinds of polypeptide in vitro obtained by hydrolysis of Euphausia superba using three different kinds of protease(papain, alkaline protease, trypsin), respectively. As can be seen from the experimental data, the antioxidant activity of polypeptide prepared by papain hydrolysis of Euphausia superba is best, followed by alkaline protease.With the response surface method to optimize the peptide preparation technology of Euphausia superba using papain,and the molecular weight of the peptide was determined by gel electrophoresis.The results show that the protein peptide has three distinct bands, the molecular weight of which is 3-7 ku. Polypeptide solution was defluorinated through the ultrafiltration system.According to molecular weight (molecular weight, MW) size into MW≥10 ku, 5~10 ku, MW≤5 ku three peptides,then we compared the strength of its antioxidant activity.In the experimental system, three different molecular weight peptides have different ability to remove superoxide anion, hydroxyl free radical and DPPH.With the increase of the concentration of peptides, the scavenging ability increased, which was obviously dose-dependent.