Objective To study the effect and mechanism of Wenyang Huoxue Formula （Formula for warming yang and activating blood circulation） on the unstable angina pectoris of acute coronary syndrome （ACS）. Methods Eighty-six cases of unstable angina pectoris of ACS in TCM syndrome of yang deficiency with blood stasis were randomized into treatment group

42 cases

and control group

44 cases. Both groups were treated with standard management

and the treatment group was administered Wenyang Huoxue Formula additionally. The clinical symptoms and signs

scores of TCM syndromes and laboratory indexes were observed and recorded before treatment and 1 week

2 weeks

3 weeks

and 4 weeks after treatment

and 1 month’s follow-up was given. Results After treatment

the clinical symptoms and symptom scores of both groups were significantly improved （P<0.05 or P<0.01）

and the clinical curative effect of the treatment group was better than that of the control group. After treatment

the level of myohemoglobin in the treatment group was reduced （P<0.05）. The levels of thromboxane B2 （TXB2） and 6-keto-prostaglandin F1α （6-keto-PGF1α） in the treatment group were significantly improved compared with before treatment （P<0.05）

and the improvement of the treatment group was superior （P<0.05）. In the duration of treatment and follow-up

there were no drug-induced changes of heart rate and rhythm

blood pressure

abnormal changes in routine blood and urine examinations

and liver and kidney functions of the patients of the two groups. Conclusion Wenyang Huoxue Formula is safe and effective in treating unstable angina pectoris of ACS

and it improves the clinical symptoms significantly. Its therapeutic mechanism is possibly related to the regulation of angioendothelial function.