Abstract: Enzymatic hydrolysis method was used to produce the angiotensin-I-converting enzyme inhibitory peptides derived from fish scales.The effects of five kinds of proteases on the hydrolysis of the fish scales were compared quantitatively according to the degree of hydrolysis, the relative molecular weight distribution, the free amino acids content and the ACE inhibitory activity of hydrolysates and neutral protease from bacillus subtilis was chosen to be the optimum protease.Box-Behnken surface methodology was used to optimize the factors affecting protease hydrolysis.The optimum hydrolytic condition for fish scales were pH6.4, temperature 50℃, E/S5%, S5% (w/v) , time 3h, and the degree of hydrolysis was 19.26%.The hydrolysate of the fish scales was rich in praline, glycine and alanine, but none tryptophan.The hydrophobic amino acids occupied 28% of the total amino acids.The relative molecular weight of most peptides was from 80 to 800, and the peptides were short with two to six amino acids.