BACKGROUND: Heart failure (HF) is characterized by a disorder of cardiomyocyte energy metabolism. Xinbao Pill (XBW), a traditional Chinese medicine formulation integrating "Liushen Pill" and "Shenfu Decoction," has been approved by China Food and Drug Administration for the treatment of HF for many years. The present study reveals a novel mechanism of XBW in HF through modulation of cardiac energy metabolism. METHODS: In vivo, XBW (60, 90, 120 mg/kg/d) and fenofibrate (100 mg/kg/d) were treated for six weeks in Sprague-Dawley rats that were stimulated by isoproterenol to induce HF. Cardiac function parameters were measured by echocardiography, and cardiac pathological changes were assessed using H&E, Masson, and WGA staining. In vitro, primary cultured neonatal rat cardiomyocytes (NRCMs) were induced by isoproterenol to investigate the effects of XBW on myocardial cell damage, mitochondrial function and fatty acid energy metabolism. The involvement of the SGLT1/AMPK/PPARα signalling axis was investigated. RESULTS: In both in vitro and in vivo models of ISO-induced HF, XBW significantly ameliorated cardiac hypertrophy cardiac fibrosis, and improved cardiac function. Significantly, XBW improved cardiac fatty acid metabolism and mitigated mitochondrial damage. Mechanistically, XBW effectively suppressed the expression of SGLT1 protein while upregulating the phosphorylation level of AMPK, ultimately facilitating the nuclear translocation of PPARα and enhancing its transcriptional activity. Knockdown of SGLT1 further enhanced cardiac energy metabolism by XBW, while overexpression of SGLT1 reversed the cardio-protective effect of XBW, highlighting that SGLT1 is probably a critical target of XBW in the regulation of cardiac fatty acid metabolism. CONCLUSIONS: XBW improves cardiac fatty acid energy metabolism to alleviate HF via SGLT1/AMPK/PPARα signalling axis.