Abstract: The technology for preparation of angiotensin-I-converting enzyme inhibitory peptides by hydrolyzing globin derived from porcine blood with pepsin was optimized by using the index of hydrolysis degree. The effects of hydrolysate in different phases of hydrolysis on the Angiotensin-I-Converting Enzyme(ACE) inhibitory activities were measured and the peptides with high ACE inhibitory activities were selected. The results indicated that: the optimum hydrolysis conditions were as follows: the amount of enzyme 0.3%, initial pH value 2.6, substrate concentration 0.7%, temperature 37℃, time 12 hours. Under those conditions the degree of globin hydrolysis was 11.85%. The peptides with optimum ACE inhibitory activity were obtained when hydrolysis time was four hours, and other factors were not changed. And in these conditions, the inhibitory rate of hydrolysate on ACE was 93.2% and the degree of globin hydrolysis was 9.64%.