Purpose: This study was performed to evaluate anti-thrombotic effect of Cheongyeoljohyeoltangkamibang extract (CYJHT). Methods: Blood flow rate through the regular volume of glass tube after the blood was diluted five times with ACD soulution. Antithrombotic effect was calculated as a percentage of the experimental animal figure protected from the paralysis of hind legs or death of the mouse that is caused from the administration of platelet aggregation regent. Results: 1. CYJHT inhibited the platelet aggregation induced by ADP, epinephrine, collagen and arachidonic acid as compared with the control group. 2. CYJHT inhibited pulmonary embolism induced by collagen and epinephrine (inhibitory rate is 50%). 3. CYJHT increased platelet number and fibrinogen amount significantly and also CYJHT shortened PT and APTT significantly as compared with the control group in thrombus model induced by dextran. 4. CYJHT increased blood flow rate insignificantly as compared with the control group in vivo. Conclusion: These results suggest that CYJHT can be useful in treating various female diseases caused by thrombosis, such as menstrual pain, menstrual disorder and so on.