Objective:To compare the effect for establishing rat model of chronic obstructive pulmonary disease(COPD)be-tween two methods,inhalation of PM2.5 and intratracheal instillation of PM2.5 suspension.Methods:A total of 30 adult rats were randomly divided into control group(group A),group fumigated with PM2.5(group B),and group instilled intratracheal-ly with PM2.5 suspension(group C).Then the lung function of rats,the counts of inflammatory cells in bronchoalveolar lavage fluid(BALF),and the pathological sections of lung tissues,were observed on different phases.Results:Compared with that in group A,the body mass in group B or group C decreased.And the tidal volume(VT)and the peak expiratory flow(PEF)de-creased.Furthermore,total cell count,lymphocyte count(L),neutrophil count(N),lymphocyte proportion(L%),and neutro-phil proportion(N%)in BALF increased.All the differences showed statistical significance(all P <0.05).Morphological de-tection showed enlarged alveolar space,disruption of alveolar septa,fusion of alveoli,and formation of emphysema in group B. And it also showed disordered arrangement of airways epithelial cells,partial airway epithelial hyperplasia,inflammatory cell infiltration and proliferation of smooth muscle in group B.Furthermore,mean linear intercept (MLI)and mean alveolar num-ber (MAN)in group B increased,while compared with that in group A.The pathological changes in group C were similar to those in group B.However,the degrees of pathological changes in group C were more severe,and most of them were acute in-juries.Conclusions:Rat model of COPD established by inhalation of PM2.5 was more reasonable than that established by intra-tracheal instillation of PM2.5 suspension.