OBJECTIVE: To clarify the role of aldose reductase inhibitor (ARI) in the high glucose-induced cardiomyocyte apoptosis and its mechanism. MATERIALS AND METHODS: In this study, H9c2 cardiomyocytes were employed as objects, high-glucose medium as stimulus, and ARI Epalrestat as a therapeutic drug. The cell apoptosis and activity changes of nitric oxide synthase (NOS), NO, and reactive oxygen species (ROS) were evaluated via Hoechst staining, enzyme-linked immunosorbent assay (ELISA), polymerase chain reaction (PCR), and Western blotting. In addition, the mitochondrial membrane potential was measured via fluorescence counting. RESULTS: Epalrestat inhibited the activity of AR to improve high glucose-induced oxidative stress in cardiomyocytes, weaken ROS activity, relieve the inhibition on NO activity, alleviate mitochondrial membrane potential damage, reduce the level of high glucose-induced cardiomyocyte apoptosis, and suppress the expression and activity of Caspase-3, thereby preventing high glucose-induced cardiomyocyte apoptosis. CONCLUSIONS: ARI protects against high glucose-induced cardiomyocyte apoptosis.