The mechanisms of quercetin-3-O-acetate (QA) and quercetin-3-O-propionate (QP) on anti-platelet aggregation were researched. The results revealed that QA and QP significantly increased the generation of cAMP and decreased free calcium concentration in platelet. But there was no significant impact on cGMP level. The mechanisms of QA and QP anti-platelet aggregation maybe related to they could increase cAMP content, and inhibit free calcium concentration promotion in platelets.