Abstract: The aim of this study was to investigate the stability of angiotensin-I-converting enzyme inhibitory peptide from loach.The ACE inhibitory activity of loach peptide (<2.5ku) didn't decrease after 2h heating below 80℃and remained at high active stability from pH2.0 to 8.0.Based on evaluation of ACE inhibitory activity, freeze drying was better than spray drying.Mg2+ promoted the angiotensin-I-converting enzyme inhibitory activity, while the Zn2+ and Mn2+ inhibited the angiotensin-I-converting enzyme inhibitory activity.Effect of glucose on the angiotensin-I-converting enzyme inhibitory activity significantly was greater than sucrose.With the increase of glucose concentration, the ACE inhibition activity gradually decreased and browned greater.Sodium chloride had no significant effect on antihypertensive activity.Peptides exhibited higher angiotensin-I-converting enzyme inhibitory activity hydrolysis by pepsin, but lower angiotensin-I-converting enzyme inhibitory activity after further hydrolysis by trypsin.Loach peptide belonged to the substrate type of ACE inhibitor.