Objective:To preliminarily explore the related biological basis of the theory of “intestinal diseases affecting lung”and treatment from lung in slow transit constipation(STC)by the changes of the lung and intestine pathology and the content of aquaporins(AQPs)based on compound diphenoxylate induced STC model. Methods20 SD rats were randomly divided into the normal group and model group,10 rats in each group with male and female in half. The normal group was fed with normal diet,and the model group was fed with diet containing compound diphenoxylate,with a course of 120 days. After modeling,the fecal amount within 24 hours,the water content in faeces and the rate of carbon propelling in small intestine of rats were measured,and the number of retained fecal particles in colon was observed. The pathological changes of lung and intestine were observed by HE staining. The expression levels of AQP1 in lung and AQP3 in intestinal tissue were determined by immunohistochemistry.  Results:Compared with the normal group,the fecal amount within 24 hours,the water content in faeces,the rate of carbon propelling in small intestine and the number of retained fecal particles in colon were significantly decreased in the model group(P<0.01). The pathological changes of lung and intestine with different degrees in rats were found in the model group. The coloring amount and degree of AQP1 in lung and AQP3 in colon in the model group were higher than those in the normal group(P<0.01).  Conclusion:The model of slow transit constipation is successfully replicated by compound diphenoxylate. The obvious pathological changes of lung and intestine are observed in the model rats,and the increasing contents of AQP1 in lung and AQP3 in intestine induce the disorder of body fluid metabolism,which may be the biological basis of the theory of “intestinal diseases affecting lung”and treatment from lung in slow transit constipation