Background/Aims: Diabetic cardiomyopathy (DCM) is a serious complication of diabetes. It is therefore crucial to elucidate the characteristic metabolic changes that occur during the development of diabetes to gain an understanding the pathogenesis of this disease and identify potential drug targets involved. Methods: 1 H nuclear magnetic resonance-based metabonomics combined with HPLC measurements were used to determine the metabolic changes in isolated cardiac tissues after 5 weeks, 9 weeks, and 15 weeks in rats treated with streptozotocin. Results: Pattern recognition analysis clearly discriminated the diabetic rats from time-matched control rats, suggesting that the metabolic profile of the diabetic group was markedly different from that of the controls. Quantitative analysis showed that the levels of energy metabolites, such as the high-energy phosphate pool (ATP and creatine), significantly decreased in a time-dependent manner. Correlation analysis revealed the inhibition of glycolysis and the tricarboxylic acid (TCA) cycle, enhanced lipid metabolism, and changes in some amino acids, which may have led to the decline in energy production in the DCM rats. Conclusions: The results indicated that the administration of energy substances or the manipulation of myocardial energy synthesis induced by increased glucose oxidation may contribute to the amelioration of cardiac dysfunction in diabetes.