Alcalase Protease was employed to hydrolyze Penaeus Vannamei head protein to prepare peptide with angiotensin Ⅰ-converting enzyme inhibitory activity.Gel column filtration chromatography was used to determine the molecular distribution of the hydrolysate.The results showed that the hydrolysate with the highest inhibition ratio was prepared under the condition of 50 ℃,pH8.5,enzyme concentration 0.3%(w/w) and 2 h.Gel filtration of the hydrolysate on Sephadex G-15 chromatogram yielded five absorbance peaks,the molecular distribution of the fractions with the most potent inhibition activity was located between 262~470,the IC50 was 0.79 mg/mL.