Abstract: The polypeptide extract was gained by enzymatic method from broccoli stems and leaves and its immunomodulatory effects had been studied. The crude protein was extracted from broccoli stems and leaves, and then the broccoli polypeptides were prepared by enzymatic methods. The hydrolysate was isolated by the method of ultrafiltration and Sephadex G-15. The molecular mass of the oligopeptide was 310 ~ 2600 Da. The animal experiments were studied on their immunity function.Oligopeptide were consecutively orally given to mice with the doses of 100, 50, 25 mg/kg·bw ( comparatively as 20, 10, 5 times of recommended human daily dosage) for 30 days. It was determinated for the humoral immune function, the cellular immune function and the mononuclear macrophage function in mice. Results showed that the high dose group ( 100 mg/kg) of broccoli peptide extracts had high conversion ability ( 0.225 + 0.040) and the ear weight were different ( 18.19 + 2.94) mg, it was significantly higher than that of control group ( p < 0.05) . Broccoli polypeptide extracts have obvious effect on the normal mice carbon clearance function, carbon clearance index were ( 0.126 + 0.052) and ( 0.136 + 0.022) , high and medium dose significantly ( p < 0.05) increased the nonspecific immune function of mice.Results showed that the broccoli polypeptide extract could enhance immunity function, which could provide basic data and the scientific reference for the deep development and comprehensive utilization of broccoli.