Abstract: Fungus polysaccharose abstracted from Cordyceps militaris was used as immunopotentiator,and was tested the effects on immune activities of the serum and lymphocyte of Penaeus chinensis.After the prawns were injected intraperitoneally by fungus polysaccharose,the phagocytic rate and index of lymphocyte,and immune activities of serum were detected.The results showed as follows:When the prawn had been injected for 48 h,the phagocytic rate of lymphocyte increased by 11.4%,the phagocytic index increased by 39.7%.The hemolytic ability and bacteriolytic ability of serum improved evidently over the control group,preserved at a high level until 96 h after injection.Hemagglutinating activities of serum of P.chinensis enhanced too.The polysaccharose could strengthen the nonspecific immunization function of P.chinensis distinctly.