Patients with severe pancreatitis have complex conditions and a long course of illness. Treatment and prevention of malnutrition is an issue that clinicians must pay attention to during the treatment of severe pancreatitis. When implementing nutritional support, it is necessary to choose the mode of nutritional support with regard to the advantages and disadvantages of enteral and parenteral nutritional support. The principle of choosing the mode of nutritional support should be that it does not stimulate the exocrine secretion of the pancreas, but also can achieve the purpose of nutritional support, and even achieve the role of nutritional pharmacology. In the process of treating severe pancreatitis, we feel that we can decide the nutritional support modality for severe pancreatitis according to the following specific methods. 1 , not to pursue a certain type of nutritional support completely. That is, do not mechanically pursue total enteral nutrition (TEN), or total parenteral nutrition (TPN). In the early stage of nutrition support, doctors who advocate parenteral nutrition support, emphasize total parenteral nutrition support; doctors who advocate enteral nutrition support, again emphasize total enteral nutrition support. In some hospitals, enteral nutrition is administered by dietitians and parenteral nutrition is administered by physicians. This tends to lead to a single mode of nutritional support. In fact total enteral and total parenteral nutrition have their own advantages and disadvantages in the process of clinical nutritional support. Clinicians should decide whether to use enteral or parenteral nutrition or a combination of both in different ratios according to the different stages of severe pancreatitis and the changes of the disease. Parenteral nutrition can achieve the purpose of nutritional support without stimulating the exocrine secretion of the pancreas, which is a more ideal form of nutritional support in the early stage of severe pancreatitis. However, the long-term use of parenteral nutrition can lead to biliary system cholestasis and liver damage. Sometimes the progressive increase of jaundice makes the surgeon to abandon parenteral nutrition support. If enteral nutrition support is not successfully started at this time, a clinical dilemma often arises. Recurrent vena cava catheter infections are also a problem for clinicians. Such vena cava catheter infections cannot be resolved by external infection control measures alone. According to the analysis of pathogenic bacteria of intravenous catheter sepsis in surgically critically ill patients, the causative organisms were found to be mostly of enteric origin. This is related to the ectopic intestinal flora. In patients with long-term parenteral nutrition, the intestinal mucosa is atrophied due to the long-term lack of intraluminal nutritional support mode of the intestinal mucosa epithelial cells lacking mucosal nutrients. This leads to impaired intestinal barrier function. Intestinal bacteria enter the bacteria continuously through the damaged intestinal mucosal barrier, causing recurrent systemic infections. If the patient also uses antibiotics for a long time, it leads to bacterial resistance. This makes the infection in patients with severe pancreatitis a more complex problem. At this time, restoring enteral nutrition, especially enteral nutrition with micro-ecological immune nutrition, may be the only way. Since enteral nutrition conforms to normal physiology, truly realizes the supply of nutrient substrate from the portal system, and can meet the nutritional needs of intestinal mucosa, enteral nutrition is an effective means to solve the infection and liver function damage combined with parenteral nutrition. When implementing enteral nutrition, the special needs of intestinal mucosal epithelium and intestinal associated lymphoid tissue (GALT) should also be considered, and arginine, glutamine, 3 polyunsaturated fatty acids and dietary fiber, and even intestinal beneficial bacteria should be added appropriately to achieve the purpose of microecological immune nutrition. However, two issues must be noted in the implementation of enteral nutrition in patients with severe pancreatitis. One is to minimize the stimulation of exocrine secretion of the pancreas, i.e., through the duodenum in order to far implement enteral nutrition. The enteral nutrition tube can be passed nasally through the pylorus with the aid of gastroscopy or under X-ray guidance, and the tip of the tube is placed in the distal part of the duodenal jugular, preferably in the high jejunum. Gastroscopy-assisted nasojejunal placement can be performed by push-in, trap placement, and foreign body forceps, respectively. In addition, a special trans-enteral nutrition tube can be placed through the gastroscopic biopsy hole. However, it requires a special enteral nutrition tube, which is slightly more expensive and complicated to operate. When placing the nasojejunal tube using the X-ray guide, the guide wire of the enteral nutrition tube can be replaced by the ultra-slip guide wire used for angiography. This makes it easier to adjust the strength of the super-slip guidewire to enter the pylorus under the instruction of the fluoroscope. It is easier to withdraw the guidewire after successful placement. When severe pancreatitis is operated for various reasons, late nutritional support challenges should be thought of, so a jejunostomy tube should be placed intraoperatively. The classical tunnel-embedded abdominal wall hanging tube jejunostomy method (Wechsler jejunostomy method) can be used, or the punctured jejunostomy method can be used. Since severe pancreatitis has varying degrees of malnutrition and low tissue healing ability, abdominal wall suspension should be performed regardless of the method used to avoid artificial jejunostomy fistula. When choosing a tube, overly thick latex tubes or myxomatous tubes should not be selected to avoid jejunostomy fistula or postoperative stenosis at the jejunal opening. Generally, a rubber tube of 10 to 14F can be chosen. When implementing enteral nutrition, start with a small amount at a uniform rate to avoid stimulation of the pancreas by nutrient fluid reflux. The gastrointestinal decompression tube can be suctioned regularly to know whether there is retention and regurgitation of enteral nutrition fluid. Due to the strong exocrine stimulation of the pancreas by whole protein and fat, it is advisable to choose short peptide low-fat formulas when selecting enteral nutrition products. In order to compensate for the energy deficiency of low-fat, manufacturers may increase the proportion of carbohydrates in enteral nutrition formulas, which may cause or aggravate hyperglycemia. However, hyperglycemia can be corrected by subcutaneous injection of insulin, which does not pose a big problem to the clinic. 2. Emphasis on timely resumption of enteral nutrition By timely, it means not to pursue premature implementation of enteral nutrition. In the field of trauma, especially burns, some studies have confirmed that early enteral nutrition can reduce patients’ hypermetabolism, reduce infection complications and lower mortality. Therefore, over the years, experts who are enthusiastic about enteral nutrition have mostly advocated the early implementation of enteral nutrition support in trauma patients. And this conclusion has been extended to early enteral nutrition support in various diseases. Through active implementation of enteral nutrition support in a large number of cases, we found that two prerequisites for successful implementation of enteral nutrition are that the patient’s intestinal function must be fully or partially restored, and there should be an appropriate amount of digestive fluid to complete the digestive function. It is possible to force the implementation too early, and if enteral nutrition can be successfully started, its usefulness is obvious, but it also comes with risks. In the early stages of severe pancreatitis, the benefits of simply achieving the word “early” often outweigh the risks. In patients with severe pancreatitis, there are different degrees of intestinal transport dysfunction in the early stage. Forced implementation of enteral nutrition is not uncommon, but it is followed by retention and retention of nutrient fluid. This leads to repeated stimulation of the pancreas and makes it difficult for pancreatic inflammation to subside as soon as possible, which can lead to prolonged illness. The exocrine function of the pancreas is impaired due to pancreatic inflammation, or the pancreatic fluid and bile are drained by surgery, or the intestinal fluid is lost due to pancreatic fistula and intestinal fistula, all of which can lead to digestive insufficiency. The enteral nutrition solution administered is often difficult to be completely digested and absorbed, and this problem is even more serious if the enteral nutrition solution used is of the whole protein type. It can be said that it is the motor and digestive insufficiency of severe pancreatitis that limits the premature implementation of enteral nutrition. Due to the limitation of motor and digestive function, the implementation of enteral nutrition may result in symptoms such as vomiting and diarrhea. In addition to the discomfort and the aforementioned hazards, such symptoms can cause loss of nutritional substrates, resulting in an actual lack of energy and protein supply. If total enteral nutrition is pursued at this time, it is actually difficult to achieve the purpose of preventing and correcting malnutrition, and even aggravate malnutrition as a result. In fact, similar phenomena have been observed in other critically ill patients in studies. Accordingly, it may lead to the misconception that enteral nutrition is difficult to implement in severe pancreatitis, and it may also lead to the neglect of enteral nutrition for a long time after one early attempt of enteral nutrition met with failure. However, the problems associated with long-term parenteral nutrition make it difficult to carry out parenteral nutrition. This puts clinical nutrition in a dilemma. 3, combined use of enteral and parenteral nutrition and timely adjustment The best way to prevent the above dilemma is to first solve the supply of nutritional substrate through parenteral nutrition. In the early stage of severe pancreatitis, enteral nutrition should be implemented cautiously, and enteral nutrition should be implemented actively in the later stage. At the time of partial recovery of intestinal function. Only partial enteral nutrition is used to achieve the purpose of intraluminal nutrition and mucosal nutrition to treat and prevent impaired intestinal barrier function. For this purpose, only 2O of the total energy supply should be provided through the intestine. Insufficient energy and protein supply can be supplemented by parenteral route. Since the total amount of sugar, fat emulsion and amino acids supplied via parenteral route is reduced, the osmotic pressure of parenteral nutrition solution is also reduced accordingly. The appropriate amount of enteral nutrition, in turn, has the effect of promoting the improvement of intestinal motility, digestion and absorption functions, thus facilitating the eventual complete restoration of enteral nutrition. Therefore, the general pattern of nutritional support for patients with severe pancreatitis without excessive complications should be total parenteral nutrition, enteral nutrition + parenteral nutrition and total enteral nutrition until the complete resumption of transoral diet. It is important to emphasize that this model cannot be implemented unchangingly in the nutritional support of severe pancreatitis. When the disease changes, the nutritional support should be adjusted accordingly. Patients with severe pancreatitis often develop abdominal abscesses or retroperitoneal infections, intra-abdominal hemorrhage, extra-pancreatic and extra-intestinal fistulas, and even multiple organ dysfunction (M0D) during the course of the disease. These complications can affect intestinal function to varying degrees. In this case, the decision to stop, partially or completely implement enteral nutrition support should be made by objective analysis of the patient’s intestinal function.I It is common to see clinical cases where enteral nutrition is used without paying attention to changes in the condition, thus aggravating the condition. The opposite phenomenon can also be seen, where the long-term use of parenteral nutrition with various antibiotics in patients with severe pancreatitis leads to infections, especially infections with multi-drug resistant bacteria to the point of being drug-free, because of the fear of stimulating the pancreas. In the aforementioned patients, the mere resumption of enteral nutrition may have led to complete control and eventual elimination of the infection. In conclusion, nutritional support for patients with severe pancreatitis is a very important part of their comprehensive treatment process. In the process of their nutritional support, neither pure total enteral and total parenteral nutrition nor the nutritional evolution patterns of total parenteral, parenteral + enteral and total enteral are demanded.