Objective:To explore the significance of platelet activation (PA) in patients with unstableangina pectoris (UA) and the effect of Xuefu Zhuyu pill (XZP, a Chinese composite recipe) on it, by wayof determining platelet membrane glycoprotein CD62P, CD41/CD45 expressions in whole blood of healthypersons and UA patients. Methods: XZP was given orally to 45 UA patients for 2 weeks. Their expressionsof CD62P and CD41/CD45 in peripheral blood were determined before and after treatment by whole bloodflow cytometry with special marked antibody, and compared with those in 10 healthy persons of the sameage as a normal control group. Results: Amount of expressions of CD62P and CD41/CD45 (FC%) in UApatients before treatment were 24.22± 7.92 and 25.89 ±8.10 respectively, all higher than those in thecontrol group (P＜0.01 and P＜0.05). After treatment, CD62P lowered to 20.42±8.01, significantlydifferent from that of before treatment(P＜0.05), and CD41/CD45 also showed a trend of lowering (P＞0.05). Platelet adhesion rate reduced significantly (P＜0.05) at the same time, as compared with that ofbefore treatment. Conclusion: Highly platelet activated state exists in UA patients. XZP could inhibitplatelet membrane glycoprotein CD62P and CD41/CD45 expressions, which might be the molecular mecha-nism of it in antagonizing PA.