The nutritional support after gastrointestinal tumor resection is often troubling to many patients. Today, I will analyze and explain the significance of nutritional support, risk assessment, preoperative and postoperative nutritional supply, etc. I. Why should we pay attention to nutritional support after gastrointestinal tumor resection? Postoperative malnutrition can lead to increased complications such as postoperative infection and poor wound healing, which can seriously affect the recovery of patients. Reasonable nutritional support is helpful to reduce postoperative complications, shorten hospitalization time and reduce hospitalization cost. What are the nutritional risks for patients after gastrointestinal tumor resection? It mainly includes 3 aspects: 1. After major resection of gastric tumor, the gastric volume is reduced, the secretion of digestive juice is insufficient, and the internal factors are reduced, which affects the intake of food and the absorption of iron, B vitamins and other nutrients, and eventually leads to the increase of malnutrition and anemia and other complications; 2. 3. Postoperative fever and infection can lead to increased stress consumption and negative nitrogen balance in the early postoperative period, which will lead to massive muscle loss and significant weight loss if nutrition supply is insufficient. What is the difference between preoperative nutrition and postoperative nutrition? Nutritional support is different for different targets, timing, route and target nutrition supply and duration. Indications: Severe nutritional deficiency, specific indicators include (1) weight loss >10% within 6 months or >5% within the last 3 months, body mass index <18 kg/m2; (2) PG-SGA score of 9, SGA grade C; (3) plasma albumin <30 g/L (without serious liver and kidney abnormalities), or expected to be unable to eat or absorb sufficient nutrition for more than 7 days after surgery or more, eating less than 60% of the target intake for more than 10 days. Timing: Start as early as possible and wait for the internal environment of the organism to stabilize before implementing nutritional support. Route: All adopt the five-step principle, that is, as long as the gastrointestinal function allows, the priority is to choose enteral nutrition (including oral nutrition supplementation) route, and patients who cannot be supported by oral nutrition should be fed by tube feeding. Fourth, special attention should be paid to the nutritional support program for the following categories of patients: 1. Patients with severe malnutrition: the risk caused by delayed surgery should be weighed against the risk of malnutrition before major surgery, and elective surgery should be given at least 10~14 days of preoperative nutritional support before surgery; the timing of postoperative nutritional support should be early EN or sequential nutritional support therapy, i.e. patients on parenteral nutrition support gradually transition to enteral nutrition. Patients with enteral nutrition support gradually transition to oral feeding, and the duration of nutritional support should wait until patients can eat by mouth to achieve more than 60% of the target nutritional supply. Therefore, patients after gastrectomy need to supplement the shortage of common food through oral supplementation of enteral nutrition for a period of time (about 1.5 months after surgery). 2. After major tumor surgery: normal food intake or enteral nutrition should be started as early as possible. Most of the patients who underwent colon resection can start the intake of light liquid food (including water) by mouth within a few hours after surgery. The diet should pay attention to the intake of easily digestible and absorbable food, and different principles of dietary transition should be adopted according to the site of resection. The European Society for Parenteral Enteral Nutrition (ESPEN) guidelines recommend that starting enteral nutrition early after major gastrointestinal surgery (within 24~48 h after surgery) is beneficial to promote gastrointestinal motility and shorten the hospital stay; if severe malnutrition exists before surgery, nutritional support should be given if the patient is expected to be unable to eat within 3~5 days or eat less than 60% of the recommended amount within 7~10 days after surgery. 3. Perioperative nutritional management: It is more complicated and should be managed by a multidisciplinary team, including oncologic surgeons, clinical dietitians, nurse practitioners and clinical pharmacists, and a clinical nutrition diagnosis and treatment process including preoperative nutritional screening, nutritional assessment, nutritional support, nutritional monitoring and post-hospital home nutritional management.