Gastric duplication malformation, also known as double stomach, is extremely rare clinically and accounts for approximately 9% of all GI malformations. The incidence of this disease has been reported in isolated cases and the incidence in the population is unknown. According to available data, the disease is more common in children and adolescents, with slightly more females than males. Symptoms examined are poor appetite, epigastric discomfort, dull pain, anemia, weight loss and malnutrition. If there is a duct of ectopic pancreas connected to both stomachs, it shows recurrent pancreatitis. If ulcers occur in both stomachs, blood may enter the intestine through the duct of ectopic pancreas and symptoms of black stool or upper gastrointestinal bleeding may appear. The abdominal examination usually reveals a cystic mass in the upper abdomen, which is superficial and may move. The examination items are: 1. Barium X-ray examination shows indentation in the greater curvature of the stomach or a round mass protruding into the gastric lumen resulting in pyloric distortion and narrowing. In rare cases, barium meal can be seen flowing into the cavity of both stomachs when they are connected to the cavity. 2. Ultrasound examination of the abdominal wall may reveal a cystic mass in the upper abdomen. Transendoscopic ultrasonography is more accurate in diagnosis. It can clearly distinguish the structure of each layer of the stomach wall and the cysts attached to the outer layer of the stomach, and can even detect new organisms in the double stomach. 3. Gastroscopy can detect cystic masses protruding into the gastric sinus or pylorus. In addition, CT and MRI can be performed. For patients with recurrent pancreatitis, the most feasible test to distinguish whether there is an ectopic pancreas and whether the duct of the ectopic pancreas is connected to both stomachs is retrograde cholangiopancreatography.