The human umbilical vein endothelial cells (HUVEC) under exponential growth phase were divided into three categories: normal group, irradiation group, and experimental group, where the irradiation group was only treated with γ-ray, and the experimental group was incubated with MgSO4 0.5 h before being treated with γ-ray. Then the HUVEC was collected at the corresponding time to be researched. The CCK-8 method was adopted to detect the cells’ survival rate, the flow cytometry was used to measure the cells’ distribution cycle and apoptosis rate, and the thiobarbituric acid (TBA) method was employed to test the level of malondialdehyde (MDA) included in HUVEC. The experimental results show that the MgSO4 with concentration below 6.25 mg?mL−1was non-toxic to HUVEC. However, the MgSO4 with concentration of 6.25 mg?mL−1can not only improve the survival rate of the HUVEC treated with γ-ray, but also alleviate the cells’ G2/M arrest cycle and reduce the cells’ apoptosis rate. Therefore, the MgSO4 has certain protective effect on the HUVEC with radiation injury.Cited