There are many reasons that lead to dark green loose stools, the common ones are physiological factors, gastric ulcer, indigestion and so on. 1. Physiological factors: consuming dark-colored vegetables such as spinach or animal blood such as pig’s blood, duck’s blood, etc., the pigment in the food can not be fully absorbed by the gastrointestinal tract, accompanied by gastrointestinal peristalsis too fast, black-green loose stools can occur. 2. Gastric ulcer: the mucous membrane of the inner wall of the stomach or the deeper layer is broken, resulting in gastrointestinal bleeding, and the color of the stool can be changed, which is black-green or dark red. 3. Dyspepsia: Under the combined effect of gastrointestinal dyskinesia, heredity, infection, mental and psychological factors, symptoms of epigastric discomfort can occur, manifested as a feeling of fullness in the upper abdomen, mostly accompanied by reflux, heartburn, black-green loose stools and other symptoms. There may be other reasons for black-green loose stools, such as colitis. It is recommended to go to the hospital as soon as possible, under the guidance of the doctor to clarify the cause of the disease, and then give standardized treatment.