AIM: To investigate effects of ischemic pre-conditioning on the liver endogenous oxidant-antioxidant system during ischemia/reperfusion injury.METHODS: Twenty-four male Sprague-Dawley rats were randomly divided into sham-operated (Sham), ischemia/reperfusion (I/R), ischemic pre-conditioning plus ischemia/reperfusion (IPC) groups. Serum ALT, AST and hyaluronic acid levels were assayed and pathologic alterations observed. Liver malondialdehyde (MDA) contents,endogenous antioxidant enzymes, superoxidase dismutase (SOD), catalase (CAT), gultathionine peroxidase (GSH-Px)activities, neutrophils accumulation marker, myeloperoxidase (MPO) activities were measured respectively.RESULTS: Compared with I/R group, sinusoidal endothelial cells as well as hepatocytes damages, as assessed biochemically and histochemically, were improved significantly in IPC group; neutrophils infiltration was also markedly reduced. In IPC group, liver peroxidation, as measured by MDA contents, was significantly decreased when compared with I/R group; endogenous antioxidant enzymes, SOD, CAT and GSH-Px activities were markedly higher than that in I/R group.CONCLUSION: Ischemic pre-conditioning exerts protective effects on both hepatic sinusoidal endothelial cells and hepatocytes during liver I/R injury. Its mechanisms may involve dimunition of neutrophils infiltration and modulation of the imbalance of endogenous oxidant-antioxidant system in the organism.