Black stools with no odor need to consider dietary, medication and disease causes. Dietary causes include consumption of animal blood products, animal liver, etc.; medication causes include taking iron, bismuth, etc.; and disease causes include gastric ulcers and duodenal ulcers. 1. Dietary causes: such as the consumption of animal blood products, animal liver, etc., this kind of food is rich in iron, will be formed under the oxidation of the intestinal tract of black stools, coupled with the patient’s low water intake, eating less dietary fiber can be caused by dry stools, resulting in stools in a grain of a grain. 2. Drugs: Some drugs can lead to stool color changes, such as taking iron, bismuth, etc., accompanied by the symptom of one grain of stool. Generally, it can be recovered after stopping the medication. 3. Disease causes: black stool suggests upper gastrointestinal bleeding, such as esophagogastric varices, gastric ulcer, duodenal ulcer, gastric cancer and other diseases. Stool routine, gastroscopy and other tests are needed to clarify. If the above situation occurs, it is recommended to consult a doctor in time to have the specific cause clarified by a professional doctor.