Oxidative stress plays a crucial role in both initiation and progression of liver injury in almost all experimental and clinical liver diseases. Antioxidative therapy is therefore an effective means of preventing and attenuating oxidative stress related liver diseases. Human paraoxonase 3 (hPON3) is a lipid-associated enzyme with antioxidant activity. In the present study, hPON3 cDNA gene was cloned into pcDNA3.1 plasmid and electro-transferred into mouse skeletal muscle to maintain a higher serum PON3 activity. After gene delivery, serum PON3 activity was about 1.4 times higher than those of control and PON3 mRNA expression was also detected in mouse skeletal muscle. To investigate the role of hPON3 in protecting mice against liver injury, subacute liver injury model was induced by repeated CCl₄ administration and hPON3 gene was delivered into mouse skeletal muscle before progression or recovery phase, respectively, of liver injury. Afterwards, the mice were euthanized to evaluate liver marker enzymes, degrees of oxidative stress and liver histological architecture in order to reveal the effects of PON3 on subacute liver injury. In both damage phases, delivery of hPON3 gene significantly reduced serum aminotransferase level and improved liver histological architecture. Moreover, transgene expression of hPON3 attenuated oxidative stress by increasing hepatic glutathione content, superoxide dismutase (SOD) activity, total antioxidant capability (T-AOC), and reducing malondialdehyde (MDA) level.