Abstract:Based on platelet aggregation induced by platelet activating factor(PAF) .the active fraction with in-hibiting effect was sereened from four spacies of Chinese drung Beimu.the bulbs of Fritillaria przewalskii, F. us-suriensis. F. anhuiensis and F. thunbergii.According to the experimental results. the active water soluble fraction of F. ussuriensis was further studied. Two nucleosides, thymidine and adenosine were isolated. Platelet aggregation as-say shows that adenosine is the chief aggregation inhibitor with 1%= 42 at 5μm. It is suggestad that nucleosides maybe the other type of active constituent besides alkaloids in the Fritiaria plants.