Objective To study the clinical efficacy of unstable angina patients with the treatment of Yixin Kangtai capsule combine with diltiazem .Methods A total of 98 patients with unstable angina were randomly divided into control group and treat-ment group ,49 in each group .The control group was given conventional anti-anginal drug therapy ;while combination group was given Yixin Kangtai capsule combine with diltiazem on the basis of conventional anti-anginal medication .The course was 30 days . After the treatment ,the symptoms of angina ,ECG ST-T ,blood viscosity and markers of endothelial function NO and ET levels were observed .Results After treatment ,the total effective rate of the combination therapy group was higher than that of the con-trol group (P< 0 .05) ;the angina attacks and its duration in combination therapy group were lower than that of control group(P<0 .05) ;the total efficiency of electrocardiogram in combination therapy group was better than that of the control group (P< 0 .05) ;blood viscosity values and ET levels of combination therapy group were reduced compared with before treatment (P < 0 .05) ,but NO levels were increased(P< 0 .05) .Conclusion Yixin Kangtai capsule combine with diltiazem have significant efficacy for unsta-ble angina pectoris ,and have protective effect on endothelial function in patients with unstable angina .