Objective: To analyze the similarities and differences of the applications of "the lung and large intestine being interior-exteriorly related"between the ancient and modern clinical practices, and to reveal the theory meaning.Method: Based on the ancient and modern medical cases database, 245 ancient medical records and 373 modern medical records were studied with the general statistical description and analysis of association rules, and the results were compared to summarize the similarities and differences of the regular pattern of syndrome and treatment on lung-large intestine related diseases in ancient and modern medical records.Results: In modern medical cases, intestinal diseases appeared with the main symptom of constipation due to deficiency of lung qi and qi stagnation of large intestine were always treated by purgation together with replenishing and restoring lung qi. In ancient medical cases, large intestine heat was always caused by lung heat and a variety of diarrhea symptoms appeared. They were always treated by clearing heat and moistening lungs. In addition, the symptom of bound stool caused by qi stagnation of large intestine due to lung qi stagnation was always treated by lowering lung qi to regulate and smooth large intestine qi. And Armeniae Amarum Semen was used by both as a core medicinal herb.Conclusion: Ascending-descending of qi movement is the core of the lung and large intestine relationship. In other words, the lung and the large intestine communicate through qi.
