Abstract: Hongdao clam with high nutritional value and regional characteristics was taken as the research object, and the enzymolysis effect of five enzymes on the clam was compared including protamex protease, flavor protease, neutral protease, alkaline protease and papain protease, using the degree of hydrolysis (DH) as the index. The results showed that the enzymolysis effect of protamex protease was better than other proteases. The effects of enzymolysis temperature, pH, material liquid ratio, enzyme dosage and enzymolysis time on the enzymatic hydrolysis were compared. Then the optimum process parameters determined by orthogonal test were as follows: enzymolysis temperature 58 ℃, enzymolysis time 6 h, initial pH7.0, material liquid ratio 1:2 (g:g) and 1000 U/g protamex, under the optimized hydrolysis conditions, the degree of hydrolysis was up to 71.03%±0.69%. The molecular weight distribution of the clam peptide was determined by high-performance liquid chromatography (HPLC) and the ratio of polypeptide molecular weight less than 1000 Da was 94.29%. The anti-hypertensive activity of clam peptide was also studied, and the results showed that the clam peptide prepared by this method had significant angiotensin converting enzyme (ACE) inhibitory activity with IC₅₀ = 0.67 mg/mL. The results of this study provide a theoretical basis for the further processing and utilization of Hongdao clams.