Objective:To observe the protective effect of Yulangsan polysaecharide(YLSPS) on diclofenac-induced liver injury in Kunming mice. Methods:The models of diclofenac-induced liver injury in mice with method of injection were used to study the pro-tective effect of YLSPS. Kunming mice were randomly divided into liver injured DICF group,NC group,YLSPS high-,middle-,low- group(600,300,150 mg/kg) and dimethyl diphenyl bicarboxylate(200 mg/kg DDB) group. The treatment groups were orally adminis-tered once per day whereas the normal and model groups were orally administered with saline for 14 d. Except normal group,all the other mice were injected intraperitoneally with DICF(50 mg/kg body weight). After fasting for 20 h,animals were sacrificed and blood,liver samples were obtained. The levels of alanine aminotransferase(ALT),aspartate aminotransferase(AST),alkaline phos-phatase(ALP),total bilirubin(TBIL),tumor necrosis factor-α(TNF-α) and interleukin-1β(IL-1β) in serum and levels of superoxide dismutase(SOD),glutathione peroxidase(GSH-Px),catalase(CAT),malondialdehyde(MDA) in liver tissue were measured. Hema-toxylineosin(HE) stain was used to examine the degree of hepatic injury. Results:Compared with model group,YLSPS could reduce the levels of ALT,AST,ALP,TBIL,MDA,TNF-α and IL-1β. The activities of GSH-Px,SOD,and CAT could be increased (P<0.05),and the degree of hepatic injury could be lessened. Conclusion:YLSPS has protective effect on diclofenac-induced liver injury in mice. The mechanism may be related to attenuat-ing free radical and inhibiting the effect on lipid peroxidation.