The objective was to report a relatively rare case of fulminant type 1 diabetes (FT1DM) complicated with acute pancreatitis (AP), to summarize the characteristics as well as experience of diagnosis and treatment, and to explore its pathogenesis. Clinical data of a case of FT1DM complicated with AP in the Department of Endocrinology of our hospital were analyzed retrospectively. A 66-year-old male presented with acute fever and abdominal pain, accompanying with the significantly elevated pancreatic enzymes, and his abdominal CT scan showed exudation around the pancreas. The clinical manifestations mentioned above were consistent with the diagnosis of AP. Five days after onset, the patient developed clinical symptoms, such as obvious thirst, polyuria, polyasthenia and fatigue. Meanwhile, his plasma glucose increased significantly and the diabetic ketoacidosis (DKA) occurred. The patient's fasting and postprandial 2 hours C peptide decreased significantly (all 0.02 μg/L), glycated hemoglobin level was not high (6%), and his islet-related autoantibodies were undetectable. Thus, the patient could be diagnosed with FT1DM. After the treatment of fasting, fluid replacement, anti-infection, somatostatin, anticoagulation and intravenous insulin sequential subcutaneous insulin pump, the patient gained the alleviation of pancreatitis, restoration of oral intake, and relatively stable blood glucose levels. Summarizing the characte-ristics of this case and reviewing the literature, FT1DM complicated with AP was relatively rare in FT1DM. Its common characteristics were described below: (1) Most cases started with AP and the blood glucose elevated within 1 week, or some cases had the simultaneously onset of AP and FT1DM. (2) The clinical course of AP was short and relieved no more than 1 week; Pancreatic imaging could completely return to normal within 1 to 4 weeks after onset. (3) The etiology of AP most was idiopathic; The elevation of pancreatic enzyme level was slight and the recovery was rapidly compared with AP of other etiologies. FT1DM could be complicated with AP, which was different from the physiological manifestations of pancreatic disease in general FT1DM patients. Virus infection mignt be the common cause of AP and FT1DM, and AP might be the early clinical manifestation of some FT1DM. The FT1DM patients developed with abdominal pain was easy to be missed, misdiagnosed and delayed, which should receive more attention in clinic.