Abstract: Preparation of red bean peptides by ultrasonic- assisted enzymatic hydrolysis and antioxidant activity were researched.On the basis of single factor experiment,hydrolysis process of preparing red bean peptides with ultrasonic assist were determined by response surface methodology. The optimal hydrolysis parameters were as follows: adding amount of Alcalase was 3.5%,ultrasonic power was 346 W,reaction temperature was 60 ℃,reaction time was 92 min and reaction p H was 8.4.Under the optimal process conditions,yield of red bean peptides was 85.84%. Antioxidant capacity was enhanced with the increase of peptides concentration. When peptides reached a certain concentration,peptides concentration was no longer the main influence factors of antioxidant capacity.