Technical Abstract: The enzymatic hydrolysis technology of rice protein and the antioxidant activity of the hydrolysate were studied. Substrate concentration,enzyme dose,pH value and temperature were selected as factors to optimize the hydrolysis parameters with single—factor and orthogonal tests. Results show the optimum condition for the enzymatic hydrolysis is as follows:substrate concentration 10%,enzyme dose 5%,pH value 6.0,temperature 60',and time 90 min.Under the optimum condition,the soluble solid content of the hydrolysate is 25.6 ms/mE,and the DPPH free radical scavenging rate is 54.5%. Moreover,the result of an experiment shows that the rice protein hydrolysate has very strong scavenging capabilities for DPPH free radical and hydroxyl radical,and their IC50 are 1.738 and 0.238 mg/mL respectively,showing a very strong reducing ability.It is concluded that hydrolysate from rice protein as natural peptide has antioxidant activity.