Insulinoma is an endocrine tumor of the pancreas, called pancreatic beta-cell tumor, and is referred to as insulinoma because of the typical symptoms of excessive insulin production. Typical manifestations are Whipple’s triad: (1) spontaneous periodic episodes of hypoglycemic symptoms, coma and its psychoneurological symptoms (such as crying, laughing, obscene speech, etc.), often in the early morning on an empty stomach or after labor; (2) blood sugar below 2.78 mmol/L at the time of episodes; (3) symptoms can disappear immediately after oral or intravenous glucose injection. Since patients often have hypoglycemia, they have to carry sugar water or cookies and other food with them, and often eat too much when they have symptoms, so most of them are fat. The possibility of the disease should be considered when typical manifestations are found. Firstly, blood glucose, insulin and C-peptide measurement should be performed to characterize the disease. Since the tumor can show obvious symptoms when it is very small, it is usually difficult to be detected by Bus or even CT. Enhanced CT is preferred, and if it is still difficult to be detected MRI or enhanced MRI is needed because the latter has better tissue resolution than CT, with the disadvantage that the examination takes longer and costs more. Insulinoma is both benign and malignant, and it is difficult to distinguish when the lesion is small. Therefore, once this disease is detected, surgery is performed as soon as possible, and most patients’ blood sugar returns to normal immediately after surgery.