The enzymatic hydrolysis of whey protein concentration for preparing antioxidant peptides was optimized using one-factor-at-a-time and orthogonal array design methods. The independent variables selected were temperature, pH, substrate concentration, and enzyme-to-substrate ratio. The responses were degree of hydrolysis, 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide anion radical scavenging capacity, and ion chelating capacity. The optimal hydrolysis conditions were found to be hydrolysis at 60 ℃ and pH 8.5 at a substrate concentration of 2.5 g/100 mL with an enzyme-to-substrate ratio of 3.5％. Furthermore, the optimized values of process parameter were experimentally validated.