The Balb/C mice were whole body irradiated with γ-rays (,60,Co, 6.5 Gy), and given human fetal muscle conditioned medium (FMCM) before and after irradiation, the protective and promoting effects on hematopoiesis in irradiated mice were observed. The results showed that FMCM given I. P (2.5~5.0 ml kg,-1, d,-1,×5 d) before 6.5 Gy whole body γ-irradiation was able to protect the colony forming unite-spleen (CFU-S), and reduce the decreases of red blood cells (RBC)white blood cells (WBC) and hemeglobin (Hb) in peripheral blood; FMCM given after irradiation could effectively promote the hemopoietic reconstruction in spleen and the increases of RBC, WBC and Hb in peripheral blood. The above results suggest that FMCM has good protective and promoting effects on reducing hematopoietic damage caused by irradiation.