Abstract: Using the protein of Cucumaria frondosa visceral mass as raw material, antio-xidant peptides were prepared by enzymatic hydrolysis with complex protease. On the basis of single factor experiments, the enzymatic hydrolysis process conditions were optimized by response surface methodology, and its antioxidant activity, molecular weight distribution and amino acid composition were analyzed. The results showed that the optimum process conditions were substrate mass fraction 4.4%, enzyme dosage 4887 U/g, pH7.0, enzymolysis temperature 56 ℃ and enzymolysis time 4.2 h. Under these conditions, the DPPH radical scavenging rate of 2 mg/mL hydrolysate was 89.18%±0.11%, the ABTS free radical scavenging rate and Fe²⁺ chelating rate of 0.5 mg/mL hydrolysate were 68.11%±0.12% and 72.59%±0.08%, the hydroxyl radical scavenging rate and reducing power of 1.5 mg/mL hydrolysate were 71.86%±0.09% and 0.7473±0.0105; Molecular weight distribution and amino acid analysis showed that the antioxidant peptides in the visceral mass of Cucumaria frondosa, peptides with a molecular weight of less than 1000 Da accounted for 94.26%, they were rich in acidic and hydrophobic amino acids and had high antioxidant activity and nutritional value. This study provides a technical reference for the development of deep processing industry of Cucumaria frondosa.