Abstract: Peptidic fractions which inhibit angiotensin I-converting enzyme ( ACE) were identified from bovine skin collagen.First, bovine skin collagen was hydrolyzed by an optimized method using pepsin and alcalase.Hydrolyzed collagen obtained the most active hydrolysate ( inhibitory against ACE with an IC50 of 0.168 mg/m L) . With an ultrafiltration by MW 5000, the most active fraction of the hydrolysate was obtained ( IC50 of 0.079 mg/m L) .After further separations with the fraction lower than MW5000 by RP-HPLC, considerable ACE inhibitory peptides were found. Two novel ACE inhibitory were identified by RP-HPLC-MS/MS. The amino acid sequences were ISVPGPM and LGPVGNPGPA, IC50 values of 0.017 mg/m L ( 24.3 μmol/L) and 0.077 mg/m L ( 87.8 μmol/L) , respectively.Finally, the digestion of the two peptides in vivo physiological environment was simulated and both of them were partly degraded. The ACE inhibitory activity of the digestive products were similar to the original polypeptides.