Aim To study the effect and mechanism of cardiovascular protection of 17 beta estrodial on coagulative and fibrinolytic system in animal model and cultured human umbilical vein endothelial cell. Methods The activity changes of tissue plasminogen activator (t PA) and plasminogen activator inhibitor (PAI 1) both in vivo and in vitro were measured by spectrophotometric assay, and the level of message RNA of them were examined by in situ hybridization. In addition, the level of fibrinogen in plasma was investigated by the instrument of automobile analysing coagulative and fibrinolytic system. The intracellular free calcium concentration in single human umbilical vein endothelial cell (hUVEC) was also determined by kinetic observation with Laster Confocal Microscope. Results In vivo, the t PA activity was decreased significantly in the group that the rats were ovariectomized for 5 weeks (OVX2 group) (P<0.05) and PAI 1 activity was increased significantly in both OVX1 (the rats ovariectomized for 3 weeks) and OVX2. Fibrinogen of plasma in OVX1 was also increased (P<0.05 vs Control). In the two groups of OVX treated with 17 beta estrodial, PAI 1 activity was decreased (P<0.01, respectively) and t PA activity was increased in OVX+17 beta estrodial (P<0.05). In situ hybridization showed PAI 1 mRNA in OVX1 tissue was higher than the control. In vitro, the t PA activity and gene expression were increased with the raising concentration of 17 beta estrodial. PAI 1 mRNA was changeless between different concentrations of 17beta estrodial. The concentration of intracellular calcium free of HUVEC was decreased in physical 17 beta estrodial. Conclusions The effect of cardiovascular protect of estrogen was associated with decrease in PAI 1, fibrinogen, and [Ca 2+ ]i , as well as increase in t PA activity and gene expression.