Abstract: AIM: To explore the protective effects and mechanism of simvastatin on hypoxia/reoxygenation-induced cardiac injury. METHODS: Cultured cardiomyocytes from neonatal rats subjected to hypoxia for 2 h and reoxygenation for 4 h were divided randomly into four groups: control group, hypoxia 2h/reoxygenation 4 h group (H/R4h), simvastatin (SIM) pretreated group (concentration: 0.1 μmol/L, 1 μmol/L, 10 μmol/L), and neutralizing antibody group of TLR4: MTS510 (10 μg/L). Cardiomyocyte apoptosis was detected by flow cytometry, concentration of LDH was measured by ELISA and expression of TLR4 protein was measured by Western blot. RESULTS: Compared with that in control and H/R4h groups, H/R-induced apoptosis was markedly attenuated in SIM group in a dose-dependent manner. Protective effects of simvastatin began at 0.1 μmol/L and the maximal effects reached at 10 μmol/L. After the addition of neutralizing antibody of TLR4, cardiocyte apoptosis and activities of LDH decreased. CONCLUSION: Simvastatin protects hypoxia/reoxygenation-induced cardiac injury in a dose-dependent manner, and the protective effects are in association with TLR4 signalling pathway.