The study aimed at testing the hypothesis that tongxinluo capsule might exert its cardioprotective effect by preventing ventricular remodeling and improving coronary microvascular function in a rat model of doxorubicin-induced dilated cardiomyopathy (DCM). Rats that survived DCM induction were randomly divided into three groups to be given 1.5 g.kg(-1).day(-1) (TXL-H, n = 9) or 0.15 g.kg(-1).day(-1) (TXL-L, n = 10) of tongxinluo, or normal saline at the same volume (DCM-C, n = 10) intragastrically. Age matched normal rats treated with normal saline were used as normal controls (NOR-C, n = 9). After four weeks of treatment, the DCM-C, TXL-H, and TXL-L groups exhibited significant cardiac dysfunction, left ventricular remodeling, and coronary microvascular dysfunction, compared with the NOR-C rats. However, myocardial functional parameters were significantly improved and microvascular density (MVD) increased in the TXL-H group compared with the DCM-C group (all P < 0.01). Left ventricular remodeling was prevented. There were close linear relationships between CVF and LVEF (r = -0.683, P < 0.05), MVD and LVEF (r = 0.895, P < 0.05), and MVD and CVF (r = -0.798, P < 0.05). It was indicated that high-dose tongxinluo effectively improved cardiac function in rat model of DCM.