Several coumarins isolated from Angelica sp. were described to show inhibitory effects against human platelet aggregation. The anti-thrombotic and anti-platelet potential was evaluated, in this paper, with the BuOH soluble fraction of Angelica dahurica root. The BuOH fraction was divided into five subfractions fr. A - E and tested in the mouse model of thrombosis. Survival was enhanced to 35% with fr. A or fr. E treated (500 mg/Kg, p.o.) group of mice compared with 5% survival of the control group. However, none of the 8 coumarin glycosides obtained from fr. A, at the conc. of 0.5 mg/ml, showed inhibitory effects against rat platelet aggregation induced by ADP or collagen.