Abstract: In this paper, antioxidant peptides were hydrolyzed from the flesh of catfish through ultrasonic- assisted method.By selecting the yield and antioxidant capacity as evaluation index, the factors that affected hydrolysate activity were investigated. The process for preparation of antioxidant peptides was optimized using response surface methodology, employing a five- level, three- variable central composite rotatable design. The optimal processing conditions obtained were as follows: ultrasonic time 42 min, ultrasonic temperature 40℃, power 320 W, holding time 3.3h. Under the conditions, the yield of peptides was 1.13%. The enzymatic hydrolysate by Alcalase showed better anti- lipid peroxidation and DPPH- scavenging ability, and the IC50 was 0.55 mg / m L and 0.69 mg / m L, respectively.