Nausea and vomiting in patients after radiotherapy are common in patients with tumors in the chest and abdomen. Because radiotherapy is a treatment method to kill tumor cells by high-energy rays, therefore, in the process of radiotherapy, high-energy rays will have certain damage to the surrounding normal tissues. In patients with thoracic and abdominal tumors, the damage of high-energy rays to normal tissues during radiotherapy is mainly manifested as the side effects of gastrointestinal tract, i.e. the rays may cause mucosal damage to the gastrointestinal tract, and at the same time, the cells in the gastrointestinal tract are actively proliferating and more sensitive to the rays, so the probability of occurrence of damage is increased.