Abstract: Objective To explore the effects of magnesium on the proliferative activity of cultured humal umbilical vein endothelial cells and its protective effects on cardiovascular system.Methods　The effect of magnesium on the proliferative activity of cultured human uambilical vein endothelial cells which were 2-3 passage.MTT assay was used for the determination of cell viability and proliferation.Results　The value of OD490 of cells of Mg²⁺ supplementation group at doses of 0.3mmol/L,0.6mmol/L,1.2mmol/L,2.4mmol/L was much higher than that of normal control group,P<0.05,and that OD 490 of cells of H_2O2+Mg²⁺ group at all doses was higher than that of H_2O2 group,P<0.05.Conclusion　Mg²⁺ supplementation stimulate the proliferation of cultured human umbilical vein endothelial cells.