Traditional Chinese medicine culture has a long history.As an important part of the theory of visceral manifestation，“interior-exterior relationship between lung and large intestine” explains that the lungs and intestines have the same origin，cooperate physiologically，and influence each other pathologically and pathologically and therapeutically.Based on the theory of “interior-exterior relationship between lung and large intestine”，this paper discusses thecorrelation between lung and intestinal substances from the aspects of meridian and collateral，body fluid metabolism，mucosal immunity and intestinal movement，so as to provide reference for clinical treatment of pulmonary and intestinal diseases.