Causes of oily stools include improper diet, steatorrhea, gastrointestinal bleeding and so on. 1. Improper diet: If the patient likes to eat greasy food, such as fat residue, braised meat or stewed fried vegetables, it will lead to excessive nutrition in the body. Excessive greasy food is digested and absorbed by the gastrointestinal tract, resulting in abnormally fast intestinal peristalsis, and excessive lipid molecules will cause oily and shiny stools. 2. Fatty diarrhea: If the patient has fatty diarrhea, the intestinal fat absorption and digestion function is reduced, and the fat molecules that can not be absorbed are mixed in the food residue and excreted, which can lead to smooth and oily stools. 3. Gastrointestinal bleeding: when there is bleeding in the gastrointestinal tract, the blood iron in the blood interacts with the sulfide in the intestinal tract to form ferrous sulfide, and the ferrous sulfide makes the stool become oily and shiny. If the patient’s stool is oily and shiny, after excluding dietary factors, you can perform fecal occult blood, gastroenteroscopy and other tests to clarify the cause of the disease, and follow the doctor’s instructions for treatment.