The symptoms of dark green stool can be divided into two main causes: physiological phenomenon and disease manifestation. Excessive consumption of green-rich foods in the daily diet can lead to a large amount of pigmented substances that cannot be absorbed and utilized by the gastrointestinal tract tissues and can only be excreted from the body through the excretory system, thus causing the phenomenon of physiological dark green stool in the human body. The common causes of digestive tract diseases that cause such adverse reactions are gastrointestinal neurosis, intestinal mucositis, intestinal flora dysbiosis, etc. When these types of diseases occur in patients, the imbalance in acidity of gastrointestinal fluid and the mixing reaction between a large amount of highly acidic tissue fluid and excreta will lead to dark green feces in patients. However, in contrast to the former, most patients with this type of disease also have complications such as abdominal distension, diarrhea, constipation, and loss of appetite.