Abstract: Objective To observe the effects of angiotensin Ⅱ （Ang Ⅱ）, angiotensin converting enzyme inhibitor （ACEI） captopril, and a specific type 1 angiotensin Ⅱ receptor （AT-1） antagonist valsartan on plasminogen activator inhibitor-1 （PAI-1） and tissue type plasminogen activator （tPA） in cultured human umbilical vein endothelial cells （HUVECs）. MethodsCultured HUVECs were incubated with Ang Ⅱ of 10^-6-10^-9mol/L for 24 hours. Captopril and valsartan were added respectively to the culture medium with or without Ang Ⅱ. Antigens and activities of PAI-1and tPA in the cultured medium were measured by enzyme linked immunosorbent assay （ELISA） and the indirect chromogenic assay. Results Compared to control, 10^-9-10^-6mol/L Ang Ⅱ markedly increases PAI-1 antigen（280±15.60 vs 83.33±10.56）ng/mL,（ P＜0.05） and activities （9.25±0.39 vs 7.53±0.33 ）IU/mL,（ P＜0.01,） in a dose dependent and time dependent manner while no changes in tPA activities were found. Valsartan inhibited the increase of PAI-1 induced by Ang Ⅱ （212.67±5.38 vs 290±6.57）ng/mL, （P＜0.01） . Conclusion Ang Ⅱ stimulated the release of PAI-1 and tPA, but the increments of PAI-1 were much more than those of tPA. The activities of tPA were not increased by Ang Ⅱ. Valsartan inhibited the effects of Ang Ⅱ induced release of PAI-1. Our findings suggest that Ang Ⅱ enhanced thrombosis by decreasing fibrinolytic activity.