Typically, the color of stool in irritable bowel syndrome may appear dark green, black and other changes. Irritable bowel syndrome is a common functional disorder of the gastrointestinal tract associated with food allergy, food intolerance, visceral hypersensitivity, abnormal gastrointestinal dynamics, and intestinal microecological imbalance. The onset of the disease is dominated by abdominal pain and abnormal defecation, and may include diarrhea, constipation, acid reflux, nausea, heartburn, urinary frequency, urinary urgency, and malaise, with chronic, recurrent, and intermittent episodes. Irritable bowel syndrome can be divided into diarrhea type, constipation type, mixed type and indeterminate type. In the diarrhea type, the color of stool is dark green and light, the shape of stool is paste-like feces or watery feces, the number of stools is small and there is a large amount of mucus; constipation type, the color of stool is black and darker, the shape of stool is hard feces or dry bulbous feces, and the amount of stools is small and dry. It is recommended that patients with irritable bowel syndrome consult a doctor for a definitive diagnosis and targeted treatment under the doctor’s guidance.