Abstract: Bioactive peptides were prepared from Undaria pinnatifida sporophyll by bionic enzymatic hydrolysis. Response surface methodology (RSM) was used to optimize the enzymatic hydrolysis process based on single factor test with the polypeptide yield and degree of hydrolysis as the main indexes, and the scavenging ability of polypeptide on three free radicals (DPPH, ABTS, OH) was evaluated. The results showed that the optimal conditions of biomimetic enzymatic hydrolysis were as follows: Ultrasonic power 720 W, ultrasonic wall breaking time 40 min, solid-liquid ratio 1:104 g/mL, pepsin dosage 6.1%, enzymatic hydrolysis time 2.5 h, trypsin dosage 5%, enzymatic hydrolysis time 3 h. Under these conditions, the polypeptide yield was 21.17% and the degree of hydrolysis was 43.07%. Enzymatic peptide had good scavenging effects on DPPH, ABTS and OH radicals with IC₅₀ values of 5.71, 1.31 and 1.35 mg/mL, respectively. The optimized bionic enzymatic hydrolysis process of Undaria pinnatifida sporophyll was reasonable and feasible, and the enzymatic peptide had good free radical scavenging ability, indicating that the enzymatic peptide had good antioxidant activity and could be used as ingredients in the development of functional food.