1. Qualitative diagnosis: (1) In line with the Whipple triad (recurrent fasting hypoglycemia; blood glucose <2.8 mmol/L at the time of attack; rapid relief of symptoms after feeding or glucose supplementation). (2) Synchronous serum insulin concentration ≥ 36 pmol/L, serum insulin level and glucose ratio > 0.3; C-reactive peptide concentration ≥ 200 pmol/L, insulinogen ≥ 5 pmol/L. (3) Starvation test extending to 72 h can be performed under close supervision if necessary. (4) Measurement of serum calcium, parathyroid hormone (PTH), gastrin, prolactin (PRL) and other hormone levels is recommended to exclude MEN. 2. Localization and diagnosis: (1) Ultrasound of the upper abdomen. Pay attention to semi-recumbent examination after drinking a lot of water, and perform sulfur hexafluoride microbubble imaging when available. (2) Upper abdominal thin-section CT or magnetic resonance (MR) plain scan with enhancement at 3-5 mm intervals. multiphase arterial thin-section scan should be emphasized for CT, and rate selective presaturation method lipid suppression technique and dynamic enhanced fast interference gradient echo (FSPGR) sequence scan are recommended for MR. The presence of liver metastatic lesions should be noted when pancreatic lesions are identified. (3) Endoscopic ultrasound pancreatic scan is feasible when available, and fine needle aspiration cytology of the tumor is performed under endoscopic ultrasound localization when necessary. (4) In cases where noninvasive examination cannot be clearly localized, selective arterial calcium-stimulated venous blood collection (ASVS) is recommended to determine insulin levels. Percutaneous transhepatic puncture portal vein cannulation segmental blood collection (PTPC) can also be performed to determine insulin levels. 3. Treatment: After the qualitative diagnosis is clear, if there is an indication for surgical exploration, it should be located as clearly as possible. The surgical route is appropriate to fully reveal the pancreas, and laparoscopic exploration and resection can be considered in medical centers with conditions. Tumor removal is the main surgical procedure. For tumors in the parenchyma of the pancreas, multiple tumors in the tail of the body of the pancreas or malignant insulinoma, local pancreatic resection is feasible, including resection of the tail of the body of the pancreas with preservation or removal of the spleen. For giant tumors (>5 cm in diameter) located in the head and leptomen of the pancreas or multiple tumors in the head of the pancreas, resection of the head of the pancreas with preservation of the duodenum, pylorus-preserving pancreaticoduodenectomy or classical pancreaticoduodenectomy is feasible. If no lesion is found in the pancreas, the liver, duodenal ligament and splenic hilum should be carefully explored. In cases where the tumor is not found, pancreatic tail resection should not be performed blindly, and the operation should be terminated after intraoperative segmental blood collection from the portal and splenic veins, and postoperative insulin measurement of the above specimens should be performed to help localize the tumor, or postoperative ASVS should be performed to locate the area where the tumor is located and then operate again. If the tumor cannot be localized, the patient should be closely followed up.