Osthole is used as antiproliferation, vasorelaxation, antihepatitis, anti-inflammatory, antiaggregatory, and antiallergic effects in traditional medicine. Recently, osthole has been shown to ameliorate insulin resistance and decrease the fasting blood glucose (FBG) in high-sucrose and high-fat induced fatty liver rats. However the mechanism of its anti-diabetes is not very understood. In this work we observe the effect of osthole on the human umbilical vein endothelial cells (HUVEC) in chronic high glucose. Our data showed that osthole reduced the production of intracellular reactive oxygen species (ROS) and enhanced the the concentration of nitric oxide (NO) of cultured media in the dysfunctional vascular endothelium induced by chronic high glucose. Our current results indicated that osthole can reduce the dysfunctional vascular endothelium.