Objective To investigate the therapeutic effect of cultivated Cordyceps sinensis on rats' chronic obstructive pulmonary disease (COPD) by inhaling cigarette and analyze on the mechanism.Methods Ten-week-old male rats were selected and divided randomly into 6 groups as control group,COPD group,pre-administrated group,post-administrated group,moderate dosage group and high dosage group.Each group has 10 animals.The experimental rats were fumigated with simple smoking exposure for 90 days to establish a COPD model.Pre-administrated group were treated with Cordyceps sinensis for two weeks before fumigation.Besides receiving two weeks' drug before fumigation,moderate dosage (2.5 g · kg-1 · d-1 ) and high dosage (5 g · kg-1 · d-1 ) were given drug for the whole fumigation period.Post-administrated.group received Cordyceps sinensis for two weeks after fumigation.The animals' pulmonary function and lung tissue pathological changes were examined and observed.The total proteins from lung tissue were collected and separated by 2-dimensional electrophosis.The different significant expression proteins were identified by MS and analyzed with NCBI data.Results The average value of airway resistance of COPD group (0.386 9 cm H2O · ml-1 · s) is higher significantly than that of control group (0.263 0 cm H2O · ml-1 · s) ( P ＜0.05).The values from pre-administrated group (0.252 5 cm H2O · ml-1 · s),moderate dosage group (0.223 3 cm H2O · ml-1 · s),high dosage group (0.184 6 cm H2O · ml-1 · s) and post-administrated group (0.301 1 cm H2O · ml-1 · s),is lower significantly than that of COPD group (all P ＜0.05).But the values from the 4 drug-treatment groups have no statistical difference when compared with that of the control group.Statistically,the pulmonary functions and pathological conditions of the treatment groups,especially high dosage group,were improved greatly when compared with that of COPD group were improved significantly.There are 14 lung tissue proteins from COPD group showing a lower expression compared with that of control group.Glutathione peroxidase,aldehyde dehydrogenase and mitochondrial aldehyde dehydrogenase precursor were returned to normal expression in high dosage group.Conclusions The cultivated Cordyceps sinensis showed a evident therapeutic effect on rats' COPD,and the mechanism might be related to inhibiting and improving the imbalance of oxidation and antioxidationin in lung tissues and modulating and improving whole body condition.