Purpose : The Purpose of this research was to investigate the effects of antithromb otic activities of Honghwadangguisan(HDS) Methods : Measured the effect which was given to 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. Each of the groups consisted in 8 mice, was divided into Normal, Control, and HBS. All of these 3 group were supplied a saline solution and after an hour the control group brought the dextran extravasated blood. Also the HDS group was dosed to the experimental mice with Oral Zonde one day before the experiment. After that, the mice were abstained from food. And then we gave a measured amount of it before an hour. Finally, it gave rise to dextran extravasated blood as well as the Control group. Results : The results were obtained as follows. In vitro, HDS inhibited platelet aggregation induced by ADP and epinephrine significantly as compared with the control group. HDS showed fibrinolytic activity insignificantly as compared with the control group. HDS reduced blood flow rate in significantly as compared with the control group. In vivo HDS inhibited pulmonary embolism induced by collagen and epinephrine (inhibitive rate 50%). HDS increased number of platelet, fibrinogen amount and shortened prothrombin time, activated partial thromboplastin time significantly but reduced blood flow rate insignificantly as compared with the control group in thrombus model induced by dextran. Conclusion : HDS is effective antithrombotic activity from experimental result.