It is normal for poop to be smelly. However, if the odor is more serious, it is not normal and may be caused by dietary factors, constipation, and intestinal diseases. 1. Dietary factors: for example, a large amount of fried, high sugar, high fat, high fat and barbecue food, may lead to a large amount of sugar and protein in the food residue, through the bacterial decomposition, will cause a large amount of ammonia, resulting in smelly stools. 2. Constipation: Constipation can lead to prolonged retention of stool in the intestines, which can also cause smelly stool. 3. Intestinal diseases: for example, intestinal inflammation or intestinal tumors, because of incomplete digestion of food, can also lead to bacterial fermentation, producing a large number of ammonia-containing substances, resulting in smelly stools. If the odor of the stool is serious, excluding dietary factors or timely treatment of constipation can not be relieved, it is recommended to consult the gastroenterology department in a timely manner, improve the colonoscopy or abdominal CT and other related examinations, to determine the cause of the disease, the cause of the treatment, and under the guidance of the doctor to actively treat the disease, so as to avoid delaying the condition.