Abstract：Functional constipation is a common clinical disease in children. It refers to the elimination of organic diseases caused by the reduction of defecation times per week， difficulty in defecation， increase of defecation time or incomplete defecation. Its pathogenesis is not clear，which is related to children's diet，psychology，lack of exercise and other factors. The three categories of etiologic factors theory of traditional Chinese medicine is to selectively formulate the corresponding clinical treatment scheme according to the patient's individual，geographical environment and climate. This paper attempts to study the pathogenesis of children's functional constipation in southern Sichuan from the perspective of three categories of etiologic factors theory of traditional Chinese medicine，in order to better serve the clinical treatment of children's constipation in southern Sichuan.