Objectives: This experimental study was carried out to prove the effect of Saenghyuldan(SHD; shengxiedan) on bone marrow failure induced by cyclophosphamide(CY) and irradiation in mice. Methods: The following were performed; immunopathology, histopathlogical findings of bone marrow and in the smear of myelocyte. hematopoietic cytokine(IL-3, GM-CSF, TPO), hematopoietic stem cell colony assay, humoral immunity(LPS mitogen response), cell-mediated immunity (Con A mitogen response) and nonspecific immunity(macrophage adherence & phagocytosis) in vitro or vivo. Results: SHD showed a protective effect on bone marrow failure induced by cyclophosphamide(CY) and irradiation in mice. SHD increased lymphoproliferative responses to LPS and Con A, and activated macrophage adherence and phagocytosis to SRBC. Conclusions: We expect that SHD can be used to treat bone marrow failure and immune suppression induced by the chemotherapy or radiation.