Panaxatriol saponin (PTS), isolated from Panax pseudo-ginseng var. notoginseng, 1~ 4mg/ml inhibited rabbit platelet aggregation induced by ADP,collagen and arachidonic acid respectively in vitro. In rat,PTS 75 ~300mg/kg intraduodenally inhibited dose-dependently platelet aggregation induced by these inducers, andalso inhibited platelet thrombonane A2 release induced by collagen,but did not affect the formation of aorticwall PGI2,PTS 50~200mg/kg significantly inhibited experimental thrombosis in rats. These results showed that the anti-thrombosis action of PTS may be due to its inhibitory action on platelet aggregation and TXA2re lease