OBJECTIVE：To compare the protective effects of different effective components of Astragali radix against DNA damage of human bone marrow mesenchymal stem cells （BMSCs）induced by ionizing radiation. METHODS ：2 Gy X-rays were used to directly irradiate BMSCs to establish a radiation model. CCK- 8 method was used to detect the effects of different mass concentrations（25，50，75，100 μg/mL）of astragalus polysaccharide ，astragalus saponin and astragalus flavonoids for 1 day before radiation + 1 to 5 days after radiation on the proliferation of BMSCs. The dose concentration and the duration of intervention after radiation were selected. The irradiated BMSCs were divided into radiation group ，astragalus polysaccharide group ，astragalus saponin group and astragalus flavonoids group. The last three groups were treated with appropriate dosage of corresponding drugs before and 2 days after radiation ，and a blank groupwas set for comparison. Cytoplasmic division arrest qq.com micronucleus method was used to detect micronucleus cell rate and cell micronucleus rate after appropriate time of was used to detect th e number of 53BP1 foci in cells after appropriare time of intervention following radiation ；the number of 53BP1 foci were compared among different time points （0.5，2，12，24 h）. RESULTS ：Compared with blank group ，OD values of BMSCs were decreased significantly in radiation group （P＜0.05 or P＜0.01）. Compared with radiation group ，the OD values of BMSCs were significantly increased when 50 μ g/mL astragalus polysaccharide，astragalus saponin and astragalus flavonoids continuously intervened radiation for 2-3 days，there was significant difference in other groups at some time point （P＜0.05 or P＜ 0.01）. After consideration ，drug concentration was determined to be 50 μg/mL，and the continuous intervention time was 2 days after radiation. Compared with blank group ，the micronucleus cell rate and cell micronucleus rate of radiation group ，astragalus polysaccharide group ，astragalus saponin group and astragalus flavonoids group increased significantly ，and the number of 53BP1 focus cluster in radiation group and astragalus polysaccharide group increased significantly （P＜0.01）. Compared with radiation group and astragalus flavonoids group ，the micronucleus cell rate ，cell micronucleus rate and the number of 53BP1 focus cluster （continued intervention for 0.5，2，12 h）in the astragalus polysaccharide group and astragalus saponin group were significantly reduced，and the micronucleus cell rate and cell micronucleus rate in the astragalus polysaccharide group were significantly lower than astragalus saponin group （P＜0.05）. 53BP1 focus cluster could not be detected 24 h later （P＜0.05）. CONCLUSIONS ： Astragalus polysaccharide and astragalus saponin both have protective effects on BMSCs DNA damage induced by radiation ，and the protective effect of astragalus polysaccharide is better than that of astragalus saponin ；astragalus flavonoids has no protective effect on radiation-induced DNA damage.