Objective To investigate the possible mechanism of Maimendong Decoction（麦门冬汤） in the treatment of idiopathic pulmonary interstitial fibrosis.Methods BABL/c mice were randomly divided into a model group

an experimental group and a control group

with 15 mice in each group.In the model group and the experimental group

bleomycin 40 mg/kg was instilled in the trachea for 5 times every 2 days to construct a mouse model of idiopathic pulmonary interstitial fibrosis.In the experimental group

after 48 hours of instilling bleomycin

the suspension of Maimendong Decoction（concentration of 0.6 g/ml） was administered 2 ml/200 g.The model group and the control group were intragastrically administered with equal volume of normal saline

once a day

gavage for 2 weeks.Pulmonary functions including peak inspiratory flow（PIF）

peak expiratory flow（PEF） and minute ventilation（MV）

soluble collagen content in lung tissue and peroxisome proliferator activated receptor γ（PPARγ） mRNA and protein expression levels of each group were measured after intervention.Results Compared with the normal group

the PIF

PEF and MV of the model group were significantly decreased

the expression of PPARγ mRNA and protein in the lung tissue decreased

and the soluble collagen was significantly increased（P < 0.05 or P < 0.01）.Compared with the model group

PIF

PEF and MV were significantly increased in the experimental group.PPARγmRNA and protein expression levels were increased in lung tissue

and soluble protein was significantly decreased（P < 0.05）.Conclusion Maimendong Decoction may improve the lung function of mice with idiopathic pulmonary fibrosis by increasing the expression of PPARγ in lung tissue and decreasing the content of soluble collagen.