Objective The study proposed an efficient and economic approach to hydrolyze whey protein isolate. Methods Using trypsin to hydrolyze the whey protein, this study investigated the influences of pH, hydrolysis temperature, enzyme-substrate ratio (E/S) and hydrolysis duration on the process of enzymatic hydrolysis. The orthogonal test method was used to design the experiments of the study. Result The optimized conditions of enzymatic hydrolysis were pH8, hydrolysis temperature 40°C,5% of E/S, and hydrolysis duration 2 hours. The hydrolysis degree was 26.5%. Conclusion The parameters identified from this study can benefit the development of whey protein.