Abstract: OBJECTIVE To analyze the in vitro immune activity of polysaccharides from mycelium and fruiting body of Cordyceps militaris.METHODS For investigating the immune activity of polysaccharide of Cordyceps militaris, RAW264.7 cell strain was chosen to supply with different concentration of polysaccharides from mycelium and fruiting body of Cordyceps militaris, and the cell proliferation index, cell's phagocytosis ability of natural red and nitric oxide release level were analyzed, respectively. The quantitative relation of concentration of polysaccharide and the in vitro immune activity was also studied.RESULTS Both of polysaccharides from mycelium and fruiting body of Cordyceps militaris could show significantly promoting effects on RAW264.7 cell growth, phagocytosis ability of natural red and release of nitric oxide, which was positively associated with the concentration polysaccharide, and no significant difference were found between the cell growth promoting effects of different polysaccharides in the same dose, but the optimal concentration with best immune activity of polysaccharides from mycelium and polysaccharides from fruiting body of Cordyceps militaris were different.CONCLUSION Both of polysaccharides from mycelium and polysaccharides from fruiting body of Cordyceps militaris can show significantly in vitro immune activity.