Defecography (DFG) is a combination of dynamic and static observation of the rectal area of the anus during “defecation” by injecting a contrast agent into the patient’s rectum. It can show the functional and organic lesions in the anorectal area and provide the basis for clinical diagnosis and treatment of constipation. This method has been used in the study of pediatric megacolon and rectal prolapse since the 1960s, and was gradually applied to clinical practice in the late 1970s. In China, clinical studies on fecal imaging were conducted in the mid-1980s, and corresponding diagnostic criteria were developed. At present, nearly 70 medical institutions in China have carried out fecal imaging, with a total of more than 10,000 cases. The contrast agent is injected into the rectum to observe changes in the morphology and mucosal image of the rectal canal after sitting still, lifting the anus, forceful evacuation and emptying, so as to understand whether there are functional and organic lesions at the exit of the rectum, such as the medical room, during the process of defecation. The barium used in fecal imaging is divided into two categories: barium sulfate suspension and semi-solid burnt agent. The barium dextrin formula is mostly made of barium sulfate powder, dry starch and water, stirred and heated in a certain proportion. At present, there are commercialized burnt contrast agent (such as Anatrast) and injection gun supply. According to the different contrast agents, the fecal contrast stay is divided into barium liquid method and barium burnt method. The advantage of the barium liquid method is that it is easy to prepare and infuse the barium, and it can show the rectal mucosa well after emptying; the disadvantage is that the natural properties of the barium liquid are far from those of feces, and the infusion into the rectum mostly flows to the proximal end, which cannot expand the rectum and cause the desire to defecate, and in this case, the forceful defecation is obviously not in line with the physiological state. The disadvantages of the barium char method are that it is cumbersome to adjust the barium char; it cannot be instilled by using high-pressure syringe; the mucous membrane after emptying is not as good as the barium liquid method. However, the nature of barium dextrin is similar to that of normal human stool, and it can accumulate in the local swollen rectum after instillation to cause the desire to defecate, which makes the defecation action natural and realistic. Therefore, it is the most widely used in clinical practice. A small amount of highly concentrated barium solution can improve and enhance the rectal mucosal coating before the injection of barium burst. The degree of X-ray transmission of the fecal sitting bucket is extremely relevant to the success or failure of the imaging. Too much light transmission will overexpose the space of the soft tissues of the buttocks, which will not only fail to show the rectal prolapse, but also affect the display of the anal canal and tailbone; too little light transmission will also make it difficult to show the rectum, anal canal and tailbone; both of them will bring difficulties to the measurement and analysis. In order to cause the soft tissue density of the buttocks similar to the surrounding environment, foreign scholars more than their own design a variety of water-containing sitting circle. China completed the DS-1 type excretion imaging device in 1985, which not only solves the problem of sitting bucket density, but also has the function of lifting and rotating, easy to use, flexible, hygienic, and the wall of the bucket is equipped with a ruler, which is consistent with the magnification of the human body on the photo, and easy to measure. Four corners of the fecal emission imaging more than the use of film combined with magnetic tape video, China is currently more film-based.