Abstract: OBJECTIVE To explore the effects of Sophora japonica water extract on the immune functions of immunosuppressive mice. METHODS Kunming mice were divided into normal group, model group, lentinus edodes polysaccharide group and low-, moderate-, high-dose Sophora japonica water extract group. The immunosuppressive mice model was produced by intraperitoneal injection of cyclophosphamide for there consecutive 3 d in each group except the normal group. After 14 d of continuous intragastric administration, white blood cells number, spleen index and thymus index were measured to evaluate the immunomodulatory effect of Sophora japonica water extract. In addition, spleen lymphocyte proliferation and NK cell activity were assayed by MTT, the levels of IL-2, IFN-γ and TNF-α in serum were measured by ELISA. RESULTS Sophora japonica water extract moderate- and high-dose groups obviously elevated the peripheral white blood cells and the immune organ coefficient, significantly increased the proliferation of spleen lymphocyte caused by LPS, obviously elevated the NK cell activity and levels of IL-2 and IFN-γ in serum of immunosuppressive mice. Sophora japonica water extract high-dose group obviously elevated the proliferation of spleen lymphocytes caused by ConA and the level of TNF-α in serum. CONCLUSION Sophora japonica water extract can enhance the immune function of immunosuppressive mice.