Radiotherapy is one of the treatment means for tumor patients, and about 60-70% of patients will receive radiotherapy in different periods of treatment. However, while tumor cells are irradiated by radiation, the surrounding normal tissues will inevitably receive a certain amount of radiation, which often causes the organism to have gastrointestinal reactions such as saliva reduction, sore throat, swallowing difficulties, abnormal nutrient metabolism, and malignant fluid, resulting in different degrees of malnutrition in patients. According to statistics, the incidence of malnutrition in malignant tumor patients is as high as 40-80%, and about 97% of tumor patients need nutritional support. And malnutrition often affects the treatment effect of patients, increases the mortality rate and complication rate of tumor-related treatment, and leads to the prolongation of hospitalization time and serious decrease of survival quality. Therefore, nutritional support for radiotherapy patients is of great importance to radiotherapy-related complications and patient prognosis. High-risk groups for malnutrition (1) head and neck tumors (nasopharyngeal cancer, pharyngeal cancer, oral tumors, etc.): oral mucosal reactions often occur after radiotherapy. Most of them appear in the 3rd week of radiotherapy, and the serious period of occurrence is the 4th-5th week of radiotherapy. Difficulty in eating after radiotherapy, pain after eating, change of taste, abnormal tongue function, masticatory function is affected, fibrosis of mandibular joint, difficulty in opening mouth, and eating disorder. Nutritional support is required. (2) Thoracic tumors (such as esophageal cancer, lung cancer, mediastinal tumors, etc.): generally, radioactive esophagitis will appear 2 weeks after the start of conventional radiotherapy, with clinical manifestations of painful swallowing or pain behind the sternum; the late reaction is usually 6 months after the end of radiotherapy, with esophageal mucosa fibrosis and lumen narrowing, mainly manifesting as choking symptoms when eating too fast, so that patients have difficulty eating and insufficient intake. Nutritional support is needed. (3) Abdominal tumor (cervical cancer, rectal cancer, etc.): Patients will have different degrees of abdominal pain, increased frequency of stool, mucus stool, blood stool and other intestinal symptoms after 1 week of radiotherapy. The disease can become chronic if the course is prolonged for more than 3 months. Severe gastrointestinal disorders require nutritional support Dietary regimen (1) Diet should be high in protein, calories, vitamins and easy to digest. (2) Protein-rich foods include: lean meat, eggs, beans, milk, etc. Dietary contraindications: avoid mechanical and chemical stimuli, spicy, salty, cold, hot and rough foods; avoid alcohol, salt cured, fried and smoked foods Symptomatic care Patients with oral mucositis should adhere to correct mouth rinsing, pay attention to oral cleaning, and drink more water. When the oropharyngeal pain can be half an hour before meals, oral dicaine sugar cubes, or lidocaine 0.2g, dexamethasone 5mg, saline 250ml preparation of mouthwash, before meals with the purpose of surface anesthesia, reduce pain for the purpose of eating. At the same time, it can be combined with Chinese herbal medicine such as honeysuckle, chrysanthemum, fat sea, maitake, etc. for treatment. Patients with radiation esophagitis should be given an easily digestible, soft, liquid or semi-liquid diet. It is not advisable to lie down immediately after eating, so as not to aggravate the burden of esophageal mucosa by food reflux. Patients are encouraged to take yogurt orally before radiotherapy, 100 grams each time, which can protect or reduce the damage to the esophageal mucosa. For patients with radiation enteritis, due to the high number of stools and water loss, patients should mainly take liquid food, such as rice porridge, green vegetable juice, fruit juice, lotus root powder, etc. If the patient has severe diarrhea and sweats a lot, give the patient more light salt water to supplement the lack of water and electrolytes in the body. Appropriately increase some fruits and vegetables, such as tomatoes, oranges, fruits, etc., which not only increase vitamins, but also play an astringent and anti-diarrheal role, but bananas and pears should not be consumed, so as not to speed up intestinal peristalsis and cause an increase in the number of diarrhea. As the condition improves, gradually increase nutrition, eat less and more meals, but should not prematurely eat greasy, fried, cold, hard, acid and vinegar food, high fiber food such as celery, leek, radish, garlic moss, soybean sprouts, etc. also should not be prematurely eaten. Usually 2 to 3 days after the stools return to normal, you can eat normally.