The recovery of hematopoiesis post-radiation injury depends on the proliferation ability of survived bone marrow hematopoietic cells (BMHCs) . In this experiment the proliferation ability of BMHCs of 4~10 Gy ,γ, irradiated mice was studied with the methods of BrdU- incorperation and CFU-GM culture. The proliferation index (PI) declined significantly at 4h post injury and kept at this low level (20% of control) with 48h. The CFU-GM could hardly be detected at 4h after 4~10 Gy radiation, hinting that there might be a phase of colonizing shock early after radiation injury. The data suggest that the proliferation ability of BMHCs is inhibited by irradiation except its direct killing effect,and this might be the basis for drugs of stimulating cell proliferation to accelerate hematopoiesis recovery after radiation injury.