Abstract: Angiotensin converting enzyme(ACE)inhibitory peptides were prepared by hydrolyzing peony seed meal and its stability was analyzed. Neutral protease hydrolysates were found to have the highest ACE inhibitory activity. Based on the results of single factor experiments,the hydrolysis conditions were optimized by the response surface methodology. The results showed that the optimum conditions for the preparation of ACE inhibitory peptides from peony seed meal were as follows:The concentration of substrate was 2%,pH7.5,dosage of enzyme was 7200 U/g,the temperature was 43℃,enzyme hydrolysis time was 2 h. The ACE inhibition rate of enzymatic hydrolysates could reach 86.93%±2.38% under these conditions. Meanwhile,the ACE inhibitory peptides had good resistance to temperature,acid and alkalinity. The ACE inhibitory activity did not change significantly(P>0.05)at the temperature of 20~100℃ and pH of 2~10(P>0.05).After simulated gastrointestinal digestion in vitro,the ACE inhibitory activity did not change significantly(P>0.05),and it still maintained a good inhibitory activity.