Purpose : To investigate the inhibitory effect of HCE on platelet aggragation and erythrocyte deformiability, we performed following experiments. Methods : Concentrated Hyulbuchukotang (HCE) was fed to rats for 10days. We compare normal group with $500{eta}{Sigma}/{eta}{Sigma}$-high dose group and $100{eta}{Sigma}/{eta}{Pi}$-low dose group. Results : HCE enhanced the blood filtration rate, erythrocyte deformiability, reduced the platelet aggreablilty and inhibited granule release from collagen stimulated platelet, the prostaglandin synthesis in platelat. Conclusion : HCE should inhibit thrombos formation due to platelet hyperaggraeability and reduction of erythrocyte defonmiability.