Objective To investigate the effects of treatment with ursodeoxycholic acid (UDCA) on intrahepatic cholestasis in rats, and to explore its mechanism. Method Rats suffering from intrahepatic cholestasis were treated with UDCA. Their serum alanine transaminase (ALT), alkaline phosphatase (ALP), total bilirubin (TBL), direct bilirubin (DBL), γ-glutamyl transpeptidase (γ-GT), total cholesterol (TCH), bile flow, total bile acid excretion, total Na+ and TCH of bile were measured before and after treatment. In addition, the changes of liver tissue under microscrope were observed and recorded. Results Compared with the control group, serum ALT, ALP, TBIL, DBL, γ-GT and TCH of rats in the treatment group decreased, while bile flow, total bile acid excretion, total Na+ and TCH decreased significantly. Degeneration of hepatocytes, infiltration of inflamed cells and prolil'eration of small bile ducts in the treatment group were improved under microscope. Conclusion UDCA may have therapeutic effects on cholestatic hepatitis. The mechanism may involve in its hydrophilicity, choleretic effect and immune modulation.