Objective To research the mechanism of Feibitong Formula （formula to treat pulmonary fibrosis）for pulmonary fibrosis.Methods Sixty rats were randomized into normal control group

model group

hormone group

Feibitong low-dose group and Feibitong high-dose group

with 12 in each.The pulmonary fibrosis models were established by intratracheal injection of bleomycin in all groups but normal control group.The hormone group

Feibitong low-dose group

Feibitong highdose group was gavaged with 3mg/kg Prednisone Tablets

10g/kg Feibitong Formula

20g/kg Feibitong Formula respectively

normal control group and model group was given 2ml distilled water 28 days after modeling.The intragastric administration lasted for 21 days.The pathological form in lung tissue was observed.The levels of laminin（LN）

transforming growth factor-β1（TGF-β1）

glutathione（GSH）

typeⅠ and typeⅢ collagens in lung tissues

matrix metalloproteinase-1（MMP-1） and tissue inhibitor of metalloproteinase-1（TIMP-1） were detected.Results Comparing with the normal control group

the levels of LN

TGF-β1

MMP-1

TIMP-1

Ⅰ and Ⅲ type collagens in lung tissues in the model group were significantly increased（P<0.05）.Comparing with the model group

the LN levels were significantly decreased in the hormone group and Feibitong high-dose group（P<0.05）.There was no significant difference between groups in the GSH level（P>0.05）.Comparing with the model group

the levels of MMP-1

TIMP-1 and typeⅠcollagen were significantly decreased in the hormone group and Feibitong high-dose and low-dose groups（P<0.05）.The MMP-1 level in the Feibitong high-dose group was significantly higher than that in the Feibitong low-dose group（P<0.05）.The TIMP-1level in the hormone group was significantly lower than that in the Feibitong low-dose group（P<0.05）.Conclusion Feibitong Formula can delay the process of pulmonary fibrosis by regulating the imbalance of MMPs/TIMPs and reducing the expressions of LN and typeⅠand typeⅢcollagens.