Motion sickness in a car is also known as motion sickness in clinic. Its etiology is complex and not yet fully clarified, including the theory of sensory conflict, the theory of neural mismatch, the theory of hypersensitivity of vestibular organs, the otolith weightlessness hypothesis, and so on. 1. Conflict theory: It is mainly considered that information from vestibular, visual and proprioceptive senses are in conflict in the brain, which leads to a kind of symptom. However, this theory cannot explain why some people are more prone to motion sickness under the same exercise environment. 2. Neurological mismatch theory: It is developed on the basis of the clean conflict theory, which suggests that there is a mismatch between the incoming visual, vestibular and proprioceptive information and the information stored in the brain, thus leading to the emergence of motion sickness. 3. Vestibular organ sensitivity theory: vestibular peripheral receptors are mainly composed of three semicircular canals and balloon and ellipsoid sacs, when the human body walking on the ground and running, the acceleration generated by these movements are within the human physiological threshold, but cycling, airplanes and ships, in a rapid movement environment, more than the human physiological threshold, which causes motion sickness. 4. Otolith weightlessness hypothesis: otolith asymmetry can also cause motion sickness, part of the population under normal circumstances, humans have adapted to bilateral otolith receptor asymmetry, so there will be no abnormal vestibular response. However, in weightlessness, otoliths are stimulated by weightlessness conditions, and bilateral otolith receptors transmit asymmetric information to the brain and cause motion sickness. In addition, patients are more prone to motion sickness in the presence of excessive fatigue, improper diet, and high temperature, high humidity, and poor ventilation.