Abstract： Objective To observe the dynamic changes in spirometry and pathology of smokeinduced chronic obstructive pulmonary disease (COPD) rat,and provide a theoretical basis for the successful establishment of COPD rat model.Methods Thirty SD rats at 8 weeks of age were randomized divided into 6 weeks smoke-exposed group (E1 group) and 6 week sham-exposed group (C1 group),12weeks smoke-exposed group (E2 group) and 12 weeks sham-exposed group (C2 group),interval smokeexpose group (normal feeding 6 weeks after smoke for 12 weeks,E3 group).Using Buxco research system to obtain the spirometry data and HE staining to observe the pathological changes of lung tissue.Results ①Compared with C1 group,FRC,IC,VC and TLC of E1 group were increased (P ＜0.05),FEV100/FVC,FEV200/FVC were reduced by 22％,11％ respectively (P ＜0.01).②Compared with C2 group,the FRC of E2 group was increased while IC,VC,TLC were decreased (P ＜0.05),FEV100/FVC and FEV200/FVC were reduced by 28％ and 21％ (P ＜0.01).③Compared with E2 group,IC,VC,TLC of E3 group were increased (P ＜ 0.05),while no difference in FEV100/FVC,FEV200/FVC.④ The pathological examination of lungs from E1 group displayed narrowed alveolar septa which was the performance of mild emphysema,and with partial infiltration of characteristic inflammatory cells.The alveolar of E2 group displayed typical performance of emphysema with infiltration of a large number of inflammatory cell surrouding bronchioles and vesseles.E3 group displayed obvious emphysema while no significant inflammation was detected.C1 and C2 group showed the structural intergity of airway epithelium and alveolar septa.Conclusions Smoking time affects the spirometry and pathology of smoke induced rat typically.With 6 weeks smoking time,the rats performed early-stage COPD while with 12 weeks smoking time performed typical COPD.