Usually after drinking red wine black stool because of the following factors: First, red wine contains glucose, red wine is a product of wine making, but also contains grape pigment, grape pigment will become black products, with feces excretion, discharge. Second, after drinking red wine will cause the precipitation of minerals, iron, iron deposited in the stool and the large intestinal tube, there will also be black stool. Third, the upper gastrointestinal bleeding, there has been gastric mucosal erosion, gastric mucosal bleeding or gastrointestinal ulcers, after drinking red wine in excess will also appear black stool, which belongs to the intestinal capillary microcirculation rupture and the clinical symptoms and performance of bleeding.