Aim To investigate the effects of 17β-estradiol andα-zearalanol on coagulation and fibrinolysis in ovariectomized rats. Methods Female Wistar rats were divided into four groups (n=9 each group): sham operated (sham), ovariectomized (OVX), ovariectomized and treated with 17β-estradiol (OVX+E₂), ovariectomized and treated withα-zearalanol(OVX+ZAL). After administration of 17β-estradiol or α-zearalanol for 5 weeks, rats were killed and plasma was collected. The following parameters were tested: the prothrombin time (PT) and the activated partial thromboplastin time (APTT), the level of fibrinogen (FG) and tissue factor (TF), the activity of tissue plasminogen activator (t-PA)as well as plasminogen activator inhibitor type 1 (PAI-1). Results Ovariectomy markedly decreased PT and the activity of t-PA, as well as increased the level of FG, TF and the activity of PAI-1 in comparision with sham operated group (p<0.05 or p<0.01). These changes were reversed by 17β-estradiol or α-zearalanol replacement. Except for PAI-1, these parameters about coagulation and fibrinolysis were similar among sham, OVX+E₂ and OVX+ZAL. There was no significant difference on the value of APTT among the four groups (P>0.05). Conclusion After ovariectomy, as the endogenous estrogen decreases, the blood is hypercoagulative than ever; treating with 17β-estradiol or α-zearalanol can reverse this change. Both 17β-estradiol and α-zearalanol have protective effects on cardiovascular system. Prior study has shown that compared with 17β-estradiol, α-zearalanol has less side effects so more attention should be paid to this natural phytoestrogen.