Objective: To investigate the mechanism of the Chinese medicine theory that Fei(Lung) and Dachang(Large Intestine) are exteriorly and interiorly related via synchronous observation on the dynamic changes of the respiratory and intestinal microflora. Methods: Forty specific pathogen free Sprague-Dawley rats were selected and randomly divided into blank(10 rats) and chronic bronchitis model groups(30 rats). The blank group rats were put into the smoke-free environment and the model group rats were put into the smoke environment in order to establish pulmonary disease(chronic bronchitis) model. Then the corresponding changes of the respiratory and intestinal microflora of the model on 20th, 50th and 70th days were synchronously observed. Results: The respiratory tract microflora showed an increase in the total aerobic and Staphylococcus aureus and reduced anaerobic amount significantly on 20th day in the respiratory tract microflora(P<0.05 or 0.01). On 50th day, total aerobic, total anaerobic amount and bifidobacterium significantly increased(P<0.05). On 70th day, Staphylococcus aureus reduced and lactobacillus increased significantly(P<0.01). The intestinal microflora showed an increase in the total aerobic, Clostridium perfringens, enterobacter and enterococcus significantly increased on 20th day(P<0.05 or 0.01). Staphylococcus aureus on 50th day increased significantly(P<0.05). Total aerobic and enterococcus increased, total anaerobic and Clostridium perfringens reduced significantly on 70th day(P<0.05 or 0.01). Conclusions: The microecosystem of respiratory tract and intestine of rat model during the pathological process showed a dynamic disorder, indicating an interaction between the lung and large intestine which may be one of the connotations as they exteriorly and interiorly related. Objective: To investigate the mechanism of the Chinese medicine theory that Fei (Lung) and Dachang (Large Intestine) are exteriorly and interiorly related via synchronous observation on the dynamic changes of the respiratory and intestinal microflora. Methods: Forty specific pathogen free Sprague-Dawley The rats were selected and randomly divided into blank (10 rats) and chronic bronchitis model groups (30 rats). The blank group rats were put into the smoke-free environment and the model group rats were put into the smoke environment in order to establish pulmonary disease: chronic bronchitis model. Then the corresponding changes of the respiratory and intestinal microflora of the model on 20th, 50th and 70th days were synchronously observed. Results: The respiratory tract microflora showed an increase in the total aerobic and Staphylococcus aureus and reduced anaerobic amount significantly on 20th day in the respiratory tract microflora (P <0.05 or 0.01). On 50th day, total aerobic, total anaer On 70th day, Staphylococcus aureus reduced and lactobacillus increased significantly (P <0.01). The intestinal microflora showed an increase in the total aerobic, Clostridium perfringens, enterobacter and enterococcus significantly increased on on 20th Total aerobic and enterococcus increased, total anaerobic and Clostridium perfringens reduced significantly on 70th day (P <0.05 or 0.01). Conclusions: The microecosystem of respiratory tract and intestine of rat model during the pathological process showed a dynamic disorder, indicating an interaction between the lung and large intestine which may be one of the connotations as they exteriorly and interiorly related.