Abstract: Enzymatic hydrolysis of corn protein powder (protein content 70%) to produce ACE inhibitory peptides, by the enzymatic screening test to determine the AS.1398 neutral protease enzyme as the best, on this basis, used the pH, temperature, substrate concentration, the amount of enzyme E∶S in the single-factor test and determined the four factors in L9 (34) orthogonal test, through vitro study to detect ACE inhibition rate and yield of peptide as indicators to determine the optimum technology conditions. The result indicated that AS. 1398 neutral protease was the best hydrolytic enzyme, when the hydrolysis time in 2h, pH7.0, temperature 50℃, 5% substrate concentration, the amount of enzyme E∶S 1.5∶100, and the maximum ACE inhibition rate was 85.65%, the yield of peptide was 58.64%.