Abstract: OBJECTIVE To compare the effects of Dendrobium officinale Kimura et Migo(DOK), Dendrobium nobile Lindl.(DNL), Dendrobium chrysotoxum Lindl.(DCL), and Dendrobium fimbriatum Hook.(DFH) on improving the immune functions on mice.METHODS The mice were orally administered with 0.25, 0.50 g·kg^-1 dosage of DOK, DNL, DCL and DFH respectively for 30 d. The T lymphocyte proliferation ability, the phagocytic index and the phagocyticrate of the murine peritoneal macrophage of mice were observed. The immunosuppressed mice induced by cyclophosphamide were orally administered with 0.25, 0.50 g·kg^-1 dosage of DOK, DNL, DCL and DFH respectively for 30 d. The number of leukocyte, lymphocytes and neutrophils in the immunosuppressed mice blood were counted under microscope.RESULTS The T lymphocyte proliferation ability were enhanced, the phagocytic index of the murine peritoneal macrophage and the number of lymphocytes were increased by 0.25, 0.50 g·kg^-1 dosage of DOK, DNL, DCL and DFH. The phagocytic rate, the number of leukocyte and neutrophils in the immune suppressed mice blood were increased by 0.25, 0.50 g·kg^-1 dosage of DOK. The phagocytic rate and the number of leukocyte were increased by 0.50 g·kg^-1 DCL and DFH. The number of leukocyte were increased by 0.50 g·kg^-1 dosage of DNL.CONCLUSION DOK, DNL, DCL and DFH all can enhance the immune functions in mice. DOK is more effective on raising the macrophage phagocytic ability and increasing the number of neutrophils in the immunosuppressed mice blood.