Abstract: The antioxidative peptides were prepared from the muscle of Pacific saury by enzymatic hydrolysis. Based on the degree of hydrolysis(DH), the content of TCA-soluble peptide, DPPH free radical scavenging rate, Fe³⁺ reducing power, ·OH radical scavenging rate and O₂⁻· radical scavenging rate, the optimal protease was selected from six kinds of commercial enzyme(neutral protease, alkaline protease, flavour protease, papain, bromelain and trypsin). Single factor experiments were carried out with five factors: Solid-liquid ratio, the amount of enzyme, enzymatic hydrolysis time, temperature and pH, and three factors (solid-liquid ratio, the amount of enzyme and enzymatic hydrolysis time) were selected to optimize the response surface methodology (RSM). And the molecular weight distribution and free amino acid content of the hydrolysate were determined under the optimal conditions. The results showed that the optimal protease was neutral protease. The influence of three factors on the antioxidant activity of the enzymatic hydrolysate were the solid-liquid ratio> the amount of enzyme> enzymatic hydrolysis time. The optimal preparation processes of the antioxidative active peptide were determined as follows: the solid-liquid ratio was 1:2.67 (mass-volume ratio, g/mL), the amount of enzyme was 0.60%, enzymatic hydrolysis time was 4.04 h, temperature was 50 ℃, and pH7.0. Under these conditions, DPPH free radical scavenging rate and Fe³⁺ reducing power were 92.33% and 0.711 (20 mg/mL), respectively, which were no significant difference with the predicted value (P>0.05). It could be seen that the antioxidative peptide peptide optimized by response surface methodology had high antioxidant activity. Under the optimal conditions, 97.87% of the components with molecular weight less than 3000 Da were the main components of the hydrolysate. A total of 16 kinds of free amino acids were detected, among which essential amino acids accounted for 39.79% and antioxidant active amino acids accounted for 37.01% of the total amino acids. This study provided some reference for the utilization of high value and the development of peptides functional food of Pacific saury.