Objective To establish an animal model of severe bone marrow type acute radiation sickness in the BALB/c mice and to provide a good foundation for further investigation of severe bone marrow type acute radiation sickness.Methods BALB/c mice were given 6.0 Gy 60Co γ-rays total body irradiation.The mice were observed twice a day.The changes in body weight,peripheral blood cell counts were recorded once every three days.Histopathological sections of femur were prepared to observe the histomorphological changes.Bone marrow cells were collected to perform colony cultivation on day 1 before irradiation,and 14 d,28 d after irradiation.Results The mice were less active three days after irradiation,but there were no vomiting and loose stools.The white blood cell counts were dropped to the nadirs (3.0 ％) 11 days after irradiation and recovered to 53.7 ％ on day 28 after irradiation.The platelet counts were dropped to the nadirs (8.1％) 14 days after irradiation and recovered to 60.4 ％ on day 28 after irradiation.Histopathological section showed that the bone marrow cavity was almost empty on day 14 after irradiation.Semi-solid bone marrow cell culture results also demonstrated that CFU-GM and CFU-Mix were obviously decreased.They were not yet fully recovered on day 28 after irradiation.All mice were still alive two months after irradiation.Conclusion A murine model of severe bone marrow type acute radiation sickness has been successfully established by exposure to 6.0 Gy 60Co γ-rays.