To explore the significance of platelet activation (PA) in patients with unstable angina pectoris (UA) and the effect of Xuefu Zhuyu pill (XZP, a Chinese composite recipe) on it, by way of determining platelet membrane glycoprotein CD62P, CD41/CD45 expressions in whole blood of healthy persons and UA patients. XZP was given orally to 45 UA patients for 2 weeks. Their expressions of CD62P and CD41/CD45 in peripheral blood were determined before and after treatment by whole blood flow cytometry with special marked antibody, and compared with those in 10 healthy persons of the same age as a normal control group. Amount of expressions of CD62P and CD41/CD45 (FC%) in UA patients before treatment were 24. 22±7. 92 and 25. 89±8.10 respectively, all higher than those in the control group (P 0.05) . Platelet adhesion rate reduced significantly (P<0.05) at the same time, as compared with that of before treatment. Highly platelet activated state exists in UA patients. XZP could inhibit platelet membrane glycoprotein CD62P and CD41/CD45 expressions, which might be the molecular mechanism of it in antagonizing PA.