Abstract: Ischemic reperfusion injury is widely involved in a variety of pathophysiological processes. In liver, ischemic reperfusion injury induced by surgery can result in hepatic function failure. Previous studies indicate that the cyclin-dependent kinase inhibitor p21 protects organs against ischemia reperfusion injury. To investigate the underlying mechanism, a model of ischemic reperfusion injury in liver was induced via oxygen-glucose deprivation and re-oxygenation (OGD/R) in hepatocytes. Our data demonstrated that the mortality rate and levels of reactive oxygen species (ROS) in hepatoma cells HepG2 (expressing wild-type p53) were significantly lower than those in p53-deficient hepatoma cells Hep3B upon OGD/R. Knockdown of p53 promoted the ROS production as well as mortality rate in HepG2 cells after OGD/R treatment. Antioxidant vitamin E markedly inhibited the ROS production and mortality rate in HepG2 cells. Furthermore, our results revealed that p53 could up-regulate the expression of its target gene p21, leading to reduced ROS production and mortality rate in HepG2 cells upon ORD/R. Thus, the p53/p21 signaling protects liver against ischemic reperfusion injury, which is probably associated with inhibition of ROS formation.