Aim To investigate the effect of Tongxinluo capsules on cardiac interstitium remodeling and left ventricular function after coronary microembolization.Methods 60 male SD rats were randomly separated into three groups:control group,coronary microembolization group and tongxinluo group,each group consisted of 20 rats.After 3 days for operation,morphological characteristics were evaluated by HE staining;after 4 weeks for operation,collagen deposition were calculated by Sirius-red staining,intramyocardial arteriole detected by immunnostaining for factor α-actin antibody,left ventricular function measured by echocardiography.Results After 3 days for operation,HE staining showed multi-focal myocardial necrosis with inflammatory cells infiltration and necrosis with more involvement in subendocardial region.After 4 weeks for operation,compared with coronary microembolization group,the area of myocardial collagen were decreased in tongxinluo group,and the density of intramyocardial arteriole increased.Left ventricular end-diastole dimension(LVEDD),left ventricular end-systolic dimension(LVESD) were smaller,left ventricular posterior wall thickness(LVPWT) thicker and left ventricular ejection fraction(LVEF) higher in tongxinluo group than those in coronary microembolization group.Conclusion Intervention with tongxinluo capsules for 4 weeks can reduce cardiac interstitium remodeling and improve left ventricular function after coronary microembolization in rats.