The vagus nerve is a parasympathetic nerve. The vagus nerve is the tenth pair of cerebral nerves and the longest cerebral nerve, and it is a mixed nerve. Its main fiber composition includes four types of nerve fibers: visceral motor, visceral sensory, and somatic motor and somatic sensory fibers. Among them, the visceral motor parasympathetic fibers are an important part of the vagus nerve, which are distributed in the trachea, lungs, heart, and organs such as the liver, pancreas, spleen, and kidneys, and mainly regulate the activities of the heart and other organs, as well as the parasympathetic smooth muscle contraction of the digestive system and the secretion of glands. The vagus nerve is only a part of the parasympathetic nerve, and only some of the fibers in the vagus nerve play the role of parasympathetic nerve. In conclusion, it is recommended to consult a doctor for standardized diagnosis and treatment when necessary.