The digestive tract is covered with a large area of mucosal epithelium. After decades of technological accumulation, lesions in the mucosal layer can now be accurately diagnosed and treated by gastroscopy, colonoscopy, small intestine microscopy and even capsule endoscopy, but for lesions of submucosal origin or gastric cancer that develops latently under the mucosal layer, a definitive diagnosis needs to be made with the help of an endoscopic ultrasound system (EUS). Pancreatic cancer likewise requires the completion of ultrasound gastroscopy to determine tumor size, invasion of blood vessels, etc. Therefore, EUS is known as the top technology in gastrointestinal endoscopy precisely because it extends the physician’s view into magical territory. Usually submucosal lesions include esophageal smooth muscle tumors, mesenchymal tumors of the gastric wall, lipomas, duodenal cysts, etc. When patients are examined by ordinary gastroscopy they will find localized abnormal elevations with a smooth surface, but the exact level and how to further treat them requires the use of ultrasound endoscopy to distinguish the level of the lesion. Deeper down, in the mediastinum outside the esophageal wall and in the abdominal organs outside the stomach wall, ultrasound endoscopy will reduce the interference of the abdominal wall, intestinal gas, and lung gas, and obtain more intuitive ultrasound images than ordinary color ultrasound, or even CT or MRI. Therefore, when encountering pancreatic occupations, bile duct stones, obstructive jaundice, and mediastinal occupations, ultrasound endoscopy is of great diagnostic value, and if necessary, pathology can be obtained by puncture Tissue results.