Ｏｂｊｅｃｔｉｖｅ　To study the effect of dexmedetomidine on lipopolysaccharide（LPS）-induced apoptosis in human umbilical vein endothelial cells.　Methods　Human umbilical vein endothelial cells were randomly divided into four group （n=20）：normal control group （group C）， dexmedetomidine group （group D）， LPS group （group L）， LPS plus dexmedetomidine group（group L+D）. The cell viability and apoptosis was measured by MTT assay and flow cytometry respectively after 24 h of cell culture. The superoxide dismutase （SOD） activity and malonaldehyde（MDA） content was measured by xanthine oxidase method and thiobarbituric acid（TBA） test respectively. The expression of cleaved Poly-ADP Ribosy polymerase-1（PARP-1） protein was detected by Western blot.　Results　The cell survival rate in group L and group L+D were 0.95±0.08 and 1.08±0.10（P＜0.05），which were decreased by 36% and 27% respectively when compared with group C. The apoptotic rate in group L and group L+D were（14.70±1.8）% and （8.80±1.1）%（P＜0.05）， which were increased by 2.6 times and 1.1 times respectively when compared with group C. SOD activity in group L and group L+D were（99±6） U/mg and（182±9） U/mg（P＜0.05），which were decreased by 53% and 14% respectively when compared with group C. MDA content in group L and group L+D were （29.9±1.8） nmol/mg and （19.3±2.1） nmol/mg（P＜0.05）， which were increased by 1.6 times and 79% respectively when compared with group C. The expression of PARP-1 protein fragment in group L and group L+D were 1.152±0.095 and 0.564±0.045（P＜0.05）， which were increased by 4.8 times and 1.8 times respectively when compared with group C. No significant difference was found in group D when compared with group C（P>0.05）.　Conclusions　Dexmedetomidine can effectively reduce LPS-induced apoptosis in human umbilical vein endothelial cells by inhibiting oxidative stress and down-regulating expression of PARP-1 protein fragment.