The management of severe acute pancreatitis (SAP) is a difficult clinical problem, and SAP is not only long in duration, but also has many complications and a high mortality rate. Patients are often unable or not allowed to eat normally due to their condition, so parenteral nutrition (PN) or enteral nutrition (EN) support becomes an important part of the overall treatment. Patients with SAP may undergo multiple surgeries during the 2-3 month course of the disease and are under constant threat of sepsis, leaving their organs in an extremely fragile state. At this time, nutritional support therapy should not only maintain the patient’s nutritional status, but also protect the function of organs from damage, so that it is not allowed to lose both. Principles of nutritional support. Many scholars have made in-depth studies on the metabolic changes of the body under stress, including the exact energy requirements, the metabolic characteristics of nutrients, and the mechanism and significance of impaired liver and intestinal barrier function. The results of these studies emphasize that nutritional support must follow the principle of “metabolic support”, that is, nutritional support must conform to the laws of metabolic changes in the body during illness, and must be based on the premise of protecting organ function; SAP is critical, and the body has obvious disturbances in the internal environment and impaired organ function, so nutritional support should be implemented more carefully at this time, It should not violate the principle, but also pay attention to “individualization”. The timing and manner of nutritional support. Regarding the starting time of nutritional support, it is currently believed that early EN can reduce the degree of systemic inflammatory response syndrome (SIRS) in patients, which may stabilize the disease, and this view has also entered the guidelines. However, early SAP patients have extensive involvement of the gastrointestinal tract and poor bowel dynamics, making EN difficult to implement. Therefore, the focus of treatment is to adjust the patient’s internal environment, including improving microcirculatory status, improving oxygen supply, anti-infection, and correcting water-electrolyte and acid-base imbalance, while actively establishing jejunal nutrition channels, gradually increasing nutrition supply and adjusting nutrition types, and paying attention to the balance between synthesis and catabolism of the body. It is worth noting that during the peak of stress, patients are in a high catabolic state due to endocrine and other factors, and it is not easy to promote anabolism even with nutritional support. During the first 2 weeks of the disease, from the perspective of “metabolic support”, the principle of “low calorie supply” should be adopted. The caloric supply should not be too much, 1500 kcal/d is appropriate, otherwise it will easily increase the burden on the liver and lead to impaired liver function. As SAP can easily damage the endocrine function of the pancreas, patients generally have hyperglycemia and need to be given strict glycemic control. In recent years, scholars at home and abroad have done a lot of research on insulin resistance after stress and found that persistent hyperglycemia can significantly increase the incidence of various infectious complications. For patients with SAP, strict control of hyperglycemia is extremely important. The implementation of parenteral nutrition (PN) provides sufficient rest for the gastrointestinal tract and reduces the exocrine secretion of the pancreas, which is positive for the control of the disease. However, there is another problem, that is, the intestinal barrier dysfunction caused by long-term fasting. Numerous experimental and clinical studies have shown that the intestinal mucosa atrophies and the intestinal barrier function becomes impaired due to the lack of food stimulation and the inability to obtain nutrients directly from food. The latter has serious consequences that can lead to the translocation of bacteria and endotoxins, resulting in toxemia or enterogenic infections. Clinical studies have confirmed that almost all of the bacterial cultures of pus secondary to SAP are Gram-negative bacteria of intestinal origin. For this problem, numerous studies have confirmed the good effect of glutamine (Gln) supplementation in preventing intestinal mucosal atrophy and protecting intestinal barrier function. The timing of EN in SAP patients depends on the functional state of the intestine and varies greatly among individuals. The most commonly used route for EN is the nasogastric tube, emphasizing that the front of the tube must reach the jejunum 10 cm below the flexural ligament. Otherwise, the input EN preparation may reflux into the duodenum and stimulate pancreatic secretion, resulting in recurrent disease. In order to make the patient tolerate EN, easily digestible peptide-containing EN preparations should be selected, and if necessary, the input concentration should be reduced (12%) and the total input volume (500~1000 ml/d). The protection of intestinal barrier function requires only 10%-20% of the total EN input to be effective. Other routes of EN are endoscopy-assisted jejunal placement (PEJ) and intraoperative jejunostomy tube, which can be considered as appropriate. The prognosis of SAP patients is a reflection of comprehensive treatment, and the role of appropriate and timely surgical management is undeniable, but proper nutritional support is also an important part of treatment that cannot be ignored.