Abstract: Objective 1.To investigate effects of glycyrrhizin in rat model of pulmonary fibrosis produced by Bleomycin..Methods Sprague Dawley rats were randomly divided into pulmonary fibrosis group,NS group,DXM、 glycyrrhizin low dose、meta-dose、high dose treatment group. All pulmonary fibrosis rats in the treatment groups were intraperitoneal injection after 28 days and last for 14 days. At the 15th days, the left lung were measured by immunity class TGF-β1,IFN-γ;the right lung was made into slice which cell apoptosis was detected. The blood-serum was measured by ELISA IFN-γ and IL-4. Results 1. The pulmonary alveolitis and fibrosis of BLM group were signifieantly highter.TGF-β1 protein expression in bronehiolar epitheliums of BLM group. was stronger and more significant deviation than in every one group（p﹤0.01）. 2. The IL-4 level of BLM group was higher than all the treatment groups,but the IFN-γ level was contrary(P<0.05). 3. Strong IFN-γ protein expression was deteeted in glycyrrhizin treatment groups. IFN-γ protein expression in glycyrrhizin low dose group was more significant deviation than in the other group（p﹤0.01）. Conclusion The glycyrrhizin less TGF-β1 protein expression and IL-4 level of pulmonary fibrosis rats，but IFN-γ was contrasty. Those evidenees suggest that glycyrrhizin has strong ability to antifibrosis.