The purposes of this study is to investigate the effect of Rhus chinensis gall extract on liver function, plasma lipid composition and antioxidant system in the obese rats with high fat diet for seven weeks. Thirty two male rats of Sprague Dawely strain were divided into four groups. they are normal group (basal diet), control group(high fat diet), III group(high fat diet with Rhus chinensis gall extract 25mg/kg body weight per day) and IV group(high fat diet with Rhus chinensis gall extract 250mg/kg body weight per day). Rats in III group and IV group were administered with Rhus chinensis gall extract accordingly. Weight gains showed a tendency to decrease in rat with Rhus chinensis gall extract group but showed no differences among treatment groups. Food intake and Food efficiency ratio were not significantly different among treatment groups. Plasma total cholesterol showed a tendency to decrease in Rhus chinensis gall extract group. HDL cholesterol showed a tendency to decrease in 25mg/kg of Rhus chinensis gall extract group. However, in the 250mg/kg of Rhus chinensis gall extract group, these values showed no significant difference compared to the control group (p<0.05). GPT activities showed no significant difference among treatment groups. GOT activities showed a tendency to decrease in the groups of Rhus chinensis gall extract groups. Lipid peroxide level was significantly higher in control group than those of normal group. In Rhus chinensis gall extract groups, lipid peroxide level showed a tendency to decrease, but glutathione peroxidase activity was progressively increased. Results of our research in this paper show that Rhus chinensis gall extract might improve liver function, antioxidant system and plasma lipid composition in rats with high fat diet.