Abstract: To improve the antioxidant activity of whey protein powder hydrolysates(WPPH),the enzymolysis technology of WPPH was optimized. WPPH hydrolysis degree and antioxidant activity(1,1-diphenyl-2-picrylhydrazol(DPPH) free radical scavenging rate,hydroxyl radical scavenging rate and total antioxidant capacity) as the indexes,trypsin and bromelain with better hydrolysis effect were screened out from four kinds of protease. And the processing was optimized by single factor and orthogonal experiments. The results showed that the optimal enzymatic conditions for the complex enzyme were bromelain and trypsin added at a ratio of 1:1 at the same time,pH6.0,temperature 50℃,enzyme material ratio 0.3%,substrate concentration 3 g/100 mL,and hydrolysis time 2.5 h. Under these conditions,the degree of WPPH hydrolysis reached 34.24%. The peptides with molecular weight below 1000 Da was over 50%. DPPH free radical scavenging rate was 91.42%±0.51%,hydroxyl radical scavenging rate was 80.85%±0.47%,antioxidant capacity(46±0.65) μmol/L. Under the enzymatic conditions determined in this study,the whey protein powder hydrolysate has strong antioxidant activity,which makes certain development and utilization value in the field of natural antioxidants and health foods.