Purple stools may be caused by physiological factors, or it may be a clinical symptom of certain diseases, such as peptic ulcer, intestinal tumors and so on. 1. Physiological factors: after eating purple potatoes, purple kale and other foods, due to the pigment in the food can not be digested and absorbed by the human body, after the formation of stools, the pigment is mixed in the stools, stools will be purple. 2. Pathologic factors: (1) Peptic ulcer: including gastric ulcer and duodenal ulcer, both of which can lead to gastrointestinal bleeding, and the red blood cells in the blood will oxidize to purple when it exists in the intestine for a long time, and then finally mixed with feces to be discharged. (2) Intestinal tumor: the tumor will infiltrate the mucosal tissue of the intestine, causing bleeding, and at the same time, the surface of the swelling will be broken, oozing out blood, and the blood will stay in the intestine, forming dark purple blood clots, which will be discharged with the stool. Discharge of purple stool may also be related to other causes, such as rupture of esophageal varices, acute gastric mucosal bleeding. If the above symptoms occur, patients are advised to go to the hospital in time for early and clear diagnosis and standardized treatment.