Objective: To investigate the diagnosis and treatment of insulinoma. Methods: The clinical data of 22 patients with insulinoma admitted from 2008 to 2013 were retrospectively analyzed. Results: Of the patients, the lesion in 21 cases (95.5%) was benign, and only in one case (4.5%) was malignant. All patients had various degrees of the symptoms of Whipple’s triad, and 4 cases had different types of neuropsychiatric symptoms. The measurement of fasting serum insulin was performed in 15 patients, in all of whom the insulin release index was higher than 0.3. The preoperative tumor detection by B-type ultrasound scan, CT examination, MRI and somatostatin receptor scintigraphy was 22.7% (5/22), 54.5% (12/22), 53.8% (7/13) and 100% (1/1), and the detection rate of intraoperative B-ultrasound (IOUS) examination was 100% (10/10), respectively. Tumor enucleation was performed in 18 patients, 2 patients underwent pancreatic body and tail resection and 2 patients received pancreatic body and tail resection plus splenectomy. After surgery, the blood sugar levels in 21 patients returned to normal, but one case showed persistent hypoglycemic symptoms due to a missed tumor located in the uncinate process of the pancreas which was found by a second surgical exploration done three months later, and then the patient became normoglycemia after tumor resection. The neuropsychiatric symptoms persisted in one patient. Pancreatic fistula occurred in one case, which was completely cured three weeks later by adequate drainage and inhibition of pancreatic secretion. Conclusion: Whipple's triad and insulin release index higher than 0.3 are the mainstay for the etiologic diagnosis of insulinoma, and preoperative CT and/or MRI plus surgical exploration and intraoperative ultrasound are sensitive for lesion localization. Surgical removal is the conventional treatment for this condition.