Aim To investigate the effect and mechanism of miR-376b-3p on proliferation and apoptosis of hypoxia reoxygenation (H/R) cardiomyocytes. Methods Cultured cardiomyocyte H9c2, hypoxia-reoxygenation method was used to simulate hypoxia reoxygenation injury in vitro, and a model of myocardial cell injury was established. Flow cytometry, Western blot, enzyme-linked immunosorbent assay(ELISA) were used to detect the apoptosis rate, apoptosis-related B lymphoblastoma-2 gene(Bcl-2), Bcl-2 related X gene (Bax) protein expression and inflammatory factors secreted tumor necrosis factor α(TNF-α), interleukin-6 (IL-6) and interleukin-17 (IL-17) in normal control group, H/R group, anti-miR-NC group, anti-miR-376b-3p group, anti-miR-376b-3p+si-NC group, anti-miR-376b-3p+si-fibroblast growth factor 21(FGF21) group. The dual luciferase reporter gene assay was used to detect the fluorescence activity. Results A cell model of hypoxia reoxygenation injury was successfully established. miR-376b-3p mRNA expression was significantly increased, FGF21 mRNA and protein expression were significantly decreased in the model group. The cell apoptosis and inflammatory factor levels of TNF-α, IL-6, IL-17 were all inhibited, as well as up-regulation of Bcl-2 protein expression, down-regulation of Bax protein expression in inhibiting miR-376b-3p group. In addition, miR-376b-3p can also target FGF21 mRNA. After inhibiting FGF21,the protective effect of inhibiting miR-376b-3p on H9c2 cells damaged by hypoxia reoxygenation was weakened. Conclusion miR-376b-3p can promote the apoptosis and inflammatory response of hypoxia reoxygenation myocardial cells, and its mechanism may be related to targeting FGF21 mRNA.