Abstract: In order to optimize the enzymatic hydrolysis conditions of trypsin hydrolysis of broccoli stem and leaf protein and to study the activity of broccoli protein peptide to reduce blood lipid,the pH,temperature,enzyme amount and substrate concentration were selected as independent variables,the degree of hydrolysis was the response value,and the response surface was used to determine the optimal enzymatic process parameters. The effect of the broccoli stem and leaf protein peptide on mouse triglyceride(TC),total cholesterol(TG),low density lipoprotein cholesterol(LDL-C)high-density lipoprotein cholesterol(HDL-C),alanine aminotransferase(ALT),aspartate aminotransferase(AST),and arteriosclerosis index(AI)were analyzed though mouse feeding experiments. Results showed that,the optimal conditions for enzymatic hydrolysis of broccoli stem and leaf protein trypsin were:pH7.5,temperature 50℃,enzyme dosage 2000 U/g,substrate concentration 4%,hydrolysis degree 22.37%±0.46%. The contents of TC and ALT in serum of broccoli stem and leaf protein peptide low dose group(300 mg/kg)were significantly different from those of model group(P<0.01). The contents of TG and LDL-C were significantly different from those of model group(P<0.05). There was no significant decrease in AST content. The contents of TC,TG,LDL-C,ALT and AST in the medium(600 mg/kg)and high(1200 mg/kg)dose groups were significantly lower than those in the model group(P<0.01). The high dose group (1200 mg/kg) had no significant effect on the content of HDL-C. The low dose group(300 mg/kg)and the medium dose group(600 mg/kg)could increase the content of HDL-C,which was significantly different from the model group(P<0.01),and was conducive to the reduction of AI index. The above results showed that broccoli stem and leaf protein peptide had good hypolipidemic activity.