Objective:To investigate the effects and molecular mechanisms of water extract of Weiqi Decoction on the growth and tube formation of human umbilical vein endothelial cells (HUVECs). MethodsThe HUVECs were divided into 6 groups and treated with water extract of Weiqi Decoction at concentrations of 0,0.125,0.25,0.5 and1 mg·ml-1 or 5-FU at concentration of 30 μmol/L,respectively. After 24 hours culture,the effects of Weiqi Decoction at different concentrations on the cell proliferation of HUVECs were detected by CCK-8 assay. The tube formation of HUVECs was detected by Matrigel assay. The protein expressions and phosphorylation levels of MAPK pathway-related proteins (ERK and p38) were detected by Western blot.  Results:The water extract of Weiqi Decoction could inhibit the survival rate of HUVECs. In addition,the water extract of Weiqi Decoction could inhibit the tube formation of HUVECs in a dose-dependent manner (P<0.01),and significantly down-regulate the protein expressions and phosphorylation levels of MAPK pathway-related proteins (ERK and p38) in HUVECs (P<0.01).  Conclusion:The water extract of Weiqi Decoction can inhibit the survival rate and tube formation of HUVECs. The mechanism may be associated with the down-regulation on the expressions and phosphorylation levels of MAPK pathway related proteins (ERK and p38).