Objective To study the effect of human umbilical cord mesenchymal stem cells (hMSCs) on the survival rate of mice with radiation-induced intestinal injury and its effect on the repair of intestinal damage.Methods Adult C57BL/6J mice were selected and divided into control group and abdomen irradiation + PBS(IR + PBS) group and abdominal irradiation+hMSCs transplantation treatment (IR+hMSCs)group.Intestinal injury model was induced by abdominal irradiation at 13 Gy of T ray and the 30-day survival rate was recorded.On the 3.5th and 5.0th day after irradiation,HE staining was used to observe changes in the villus structure and thc number of intestinal crypts in each segment of the small intestine (duodenum,jejunum,and ileum).Results The survival rate of IR+hMSCs group was significantly higher than that of IR+PBS group (P＜0.05).On the 3.5th day after 13 Gy of abdomen irradiation,the duodenum,cavities and ileum villus in IR+PBS group were all fractured,the length was shortened,and the numbers were sparse when compared with the control group,while the hMSCs reduced the intestinal damage.On the 5.0th day after irradiation,the structural integrity of the small intestine in IR+PBS group was repaired slightly,but it still more serious than that of IR+hMSCs group (P＜0.01).The amount of intestine crypts were significantly higher in IR+hMSCs group than that of IR+PBS group,but were significantly lower than that of control group (P＜0.01) at 3.5th day and 5.0th day after radiation.Conclusion Transplantation of hMSCs can improve the survival rate and promote the repairation of intestinal injury induced by radiation in mice.MSCs are hopeful to be used on the treatment of radiation-induced intestinal injury.