Abstract: OBJECTIVE To study the effects of effective constituent of Cortex Moutan on platelet aggregation and blood coagulation in rabbits. METHODS Each index was measured by turbidimetric method and blood coagulation time. RESULTS High-dosage, middle-dosage and low-dosage of the administration of paeonol and paeoniflorin(paeonol 50 mg·kg^-1+paeoniflorin 12.5 mg·kg^-1, paeonol 25 mg·kg^-1+paeoniflorin 6.25 mg·kg^-1, paeonol 12.5 mg·kg^-1+paeoniflorin 3.125 mg·kg^-1), can significantly depress blood coagulation in rabbits derived by the collogen, adenosine diphosphate, arachidonic acid. High-dosage and middle-dosage of the administration of paeonol and paeoniflorin prominently prolong the plasma thrombin time and clotting time. CONCLUSION Effective constituent paeonol and paeoniflorin of Cortex Moutan can improve the platelet aggregation and blood coagulation in rabbits, provide the theory for clinical application.