Juvenile three-keeled pond turtles (Chinemys reevesii) were fed diets supplemented with vitamin C (Vc)at doses of 0 (basal diet,Vc0),100 (Vcl00),200 (Vc200),500 (Vc500) and 2500 (Vc2500) mg/kg diets at 28℃for 4 weeks,respectively.Then,the water temperature was gradually reduced to 10℃,and the turtles were induced into hibernation.Liver tissue samples were collected at three time points:start of hibernation (T1),4 and 6 weekshibernation (T2 and T3).A control group fed with the basal diet was set to parallel the whole treatment process,but reared at 28℃ constantly.The results showed that hibernation mildly affected the antioxidant system and the influence varied with hibernating time.Hepatic malondialdehyde content of the Vcl00 group was significantly lower than that of the other groups at T1.At T2,hepatic MDA in the groups of Vc500 and Vc2500 decreased significantly,while no clear differences were found among all groups at T3.The activities ofantioxidant enzymes showed a positive correlation with dietary Vc dose before hibernation.After hibernation,total antioxidant capability was not affected by Vc.Superoxide dismutase activity became similar in different groups at T2,but decreased in higher Vc groups (≥ 200 mg/kg) at T3.Glutathione peroxidase and glutathione-S-transferase activities decreased significantly with dietary Ve supplementation (≥ 100 mg/kg) at T2,but recovered at T3.The result indicates that under normal rearing condition,low dietary Vc supplementation (＜ 100 mg/kg) might be beneficial to the antioxidant defense system.The effect of dietary Vc on the antioxidant defense system differed during hibernation.