The full name of gastroscopy is upper gastrointestinal endoscopy, which is a long, thin tube with a diameter of about 1cm wrapped in black plastic with a light-guiding fiber, the front end of which is equipped with an endoscope sticking out of the mouth into the esophagus of the subject via the stomach and duodenum, and through the strong light emitted by the light source, the light can be turned by the light-guiding fiber, and the physician can clearly observe the health status of various parts of the upper gastrointestinal tract from the other end. Gastroscopy is currently the most reliable method for diagnosing esophageal, gastric and duodenal diseases, and cannot be replaced by any other methods, including upper gastrointestinal barium angiography, electrogram and color ultrasound of the gastrointestinal tract. Those who undergo gastroscopy should fast for at least 5 hours, preferably in the morning on an empty stomach, and in the case of patients with pyloric obstruction, they should fast for 2 to 3 days and undergo gastric lavage treatment if necessary. The patient should communicate well with the doctor to eliminate nervousness and fear and fully understand the necessity, safety and methods of gastroscopy in order to obtain cooperation with the examining doctor. Routinely spray the pharynx with 2% lidocaine 2 to 3 times or swallow a mouthful of 1% lidocaine syrup (about 10 ml) 5 to 10 minutes before gastroscopy to play the role of local anesthesia. Before the examination, the patient loosens the collar and belt, removes the denture, lies on the examination bed in the left lateral position, relaxes the whole body, the lower limbs are half flexed, the teeth gently clench the dental pad, takes a deep breath with the nose, and completes the examination according to the physician’s orders and prompts after entering the mirror.