The hypoxia/reoxygenation injury model was established in rat cardiomyocytes to investigate the influence of microRNA-21 on apoptosis and autophagy in rat cardiomyocytes exposed to hypoxia/reoxygenation injury. According to RT-PCR, miR-21 was up-regulated(P < 0.05) in myocardial cells after hypoxia/reoxygenation injury. Moreover, myocardial apoptosis was aggravated according to flow cytometry. According to RT-PCR and Western blot, p62 was down-regulated whereas beclin-1 was up-regulated in cardiomyocytes (P < 0.05) after hypoxia/reoxygenation injury. These consequences inditicated that hypoxia reoxygenation induced abnormal myocardial apoptosis and autophagy. miR-21 mimic or inhibitor were transfected into cardiomyocytes via liposome. MiR-21 mimic transfection significantly enhanced myocardial apoptosis (P < 0.05), up-regulated expression of p62, and down-regulated of expression of beclin-1in myocardial cells in rat cardiomyocytes(P < 0.05), while miR-21 inhibitor transfection caused opposite effects. These data suggested that miR-21 in rat cardiomyocytes exposed to myocardial hypoxia reoxygenation injury can accelerate cell apoptosis and inhibit cell autophagy. Bioinformatics projections shown that Rab11a 3'-UTR contains a binding site for miR-21. Dual luciferase report gene assay system, coupled with the overexpression of Rab11a assay validated that Rab11a is one of miR-21 target genes. Overexpression of Rab11a significantly attenuated myocardial apoptosis，up-regulation of p62 and down-regulation of beclin-1 induced by miR-21in hypoxia/reoxygenation injury. In conclusion, miR-21 can promote myocardial apoptosis and inhibit myocardial autophagy by negative regulating Rab11a in rat cardiomyocytes exposed to hypoxia/reoxygenation injury.This research proposes a new strategy for the prevention and treatment of myocardial ischemia-reperfusion injury.