Vagal excitation causes diarrhea because vagal excitation stimulates the gastrointestinal tract, causing it to move faster, thus causing diarrhea. The vagus nerve innervates various organs and systems in the body, including the circulatory system, respiratory system, and digestive system. Vagus nerve excitation has an obvious effect on the gastrointestinal tract. The release of a large amount of acetylcholine from the nerve endings leads to a strong contraction of the smooth muscles of the gastrointestinal tract as well as an increase in the secretion of digestive juices, which promotes gastrointestinal peristalsis. Therefore, vagus nerve excitation can appear defecation, hunger, etc., but if the secretion of digestive juices is too vigorous, abdominal pain, diarrhea, etc., and in severe cases, even peptic ulcers can occur, leading to bleeding, perforation and other serious digestive tract disease complications. Therefore, excessive stimulation of the vagus nerve should be avoided to avoid gastrointestinal damage. Vagus nerve excitation caused by diarrhea should be timely medical treatment, according to the condition of reasonable treatment, to lift the stimulus, so as not to cause adverse effects on the body.