Objective: To investigate the protective effect of sinomenine against renal damage caused by obstructive jaundice (OJ) in rats and the mechanism. Methods: Twenty-four rats were equally randomized into sham operation group, model group and sinomenine treatment group, and rats in the latter two groups underwent ligation and division of the common bile duct to create OJ model. From the first day after operation, rats in sinomenine treatment group were given sinomenine (80 mg/kg) by daily gavage, while those rats in sham operation group and model group received normal saline of the same volume administered in the same manner instead. On the 8th day after operation, all rats in each group were sacrificed to obtain the blood samples for measurement of the serum urea nitrogen (SUN) and serum creatinine (Scr) levels, and to harvest the renal tissues for pathological examination, and determination of renal malondialdehyde (MDA) and myeloperoxidase (MPO) concentration, and total antioxidant capacity (T-AOC) as well as the protein and mRNA expression of transforming growth factor-β1 (TGF-β1). Results: Except for the sham operation group, all rats in the other two groups exhibited the OJ manifestations and evident pathological changes of renal injury which in sinomenine treatment group were milder than those in model group. Compared with sham operation group, in the other two groups, the SUN and Scr levels were significantly increased, the renal MDA and MPO levels and TGF-β1 protein and mRNA expression levels were significantly increased, while the T-AOC was significantly decreased (all P<0.05), whereas the changing amplitudes in all above parameters in sinomenine treatment group were significantly less than those in model group (all P<0.05). Conclusion: Sinomenine has protective effect against renal injury in OJ rats, and the mechanism may be associated with its antioxidation effects and inhibition of TGF-β1 expression.