Aim To investigate the effect of miR-499a-5p on hydrogen peroxide(H₂O₂)-induced proliferation and apoptosis of cardiomyocytes H9c2, and to explore its mechanism. Methods Cell viability kit (CCK-8) was used to detect the survival rate of H9c2 cells treated with different concentrations of H₂O₂ (0,0, 0,0 μmol/L) for 6 h, and 400 μmol/L treated H9c2 cells were selected as a model group. The model group cells were divided into miR-NC group, miR-499a-5p group, si-NC group, si-APC group, miR-499a-5p+pcDNA group, miR-499a-5p+pcDNA-APC group. Flow cytometry, western blotting(Western blot) and enzyme linked immunosorbent assay (ELISA) were used to detect the survival rate, apoptosis rate, reactive oxygen species(ROS), superoxide dismutase (SOD), melondialodehyde(MDA) and proliferation-related protein expression proliferating cell nuclear antigen(PCNA), cyclins depend on kinase inhibitors(P21),Bü lymphoblastoma-2(Bcl-2),Xü gene associated with Bcl-2(Bax)of each group. Results H₂O₂(0,0, 0,0 μmol/L) inhibited the survival of H9c2 cells in a concentration-dependent manner with an optimal concentration of 400 μmol/L. The expression of miR-499a-5p was significantly decreased and the expression of APC was significantly increased in the model group. Overexpression of miR-499a-5p and inhibition of APC significantly attenuated H₂O₂-induced proliferation inhibition, apoptosis promotion and oxidation stress of H9c2 cells. miR-499a-5p can also target inhibition of APC. Overexpression of APC reversed the damage of H₂O₂-induced cardiomyocytes by miR-499a-5p.Conclusions miR-499a-5p can regulate the proliferation, apoptosis and oxidative stress of cardiomyocytes induced by H₂O₂. The mechanism is related to the targeted inhibition of APC, which will provide a new target for the treatment of myocardial cell injury induced by oxidative stress.