Abstract: Objective To investigate the effect of uric acid (UA) on the expression of endothelial nitric oxide synthase (eNOS) and the production of nitric oxide in cultured human umbilical vein endothelial cells (HUVECs). Methods HUVECs were incubated with different concentration of UA (0、5、10、15、20mg/dl) and 50mg/L ox-LDL（as positive control） for 24h、48h and 72h.. Then, eNOS mRNA was detected by real-time PCR. The expression of eNOS protein was observed by western blot. NO in supernatant medium was analyzed by Enzymic method. Results UA 5mg/dl group could increase the expression of eNOS mRNA of HUVECs ,compared with placebo control group(P<0.05). While the concentration of UA increasing and time lasting, the expression of eNOS and the production of NO were decreasing significantly(72h NO2-/NO3- is 0.52±0.18 versus 1.00±0.1 for 2 mg/L versus control， P<0.05), the same with ox-LDL. Conclusion UA inhibited the expression of eNOS and the production of NO of HUVECs in a dose-dependent and time-dependent manner. It suggested that UA can damage the function of endothelial cells and may influence genesis and development of cardiovascular diseases.