General electronic gastroscopy uses ordinary light to observe esophageal and gastric mucosa. If the lesions appearing in esophagus and stomach are small or early, ordinary electronic gastroscopy cannot distinguish them from normal mucosa because the color of lesion site and normal esophageal and gastric mucosa is basically the same under ordinary gastroscopy, so it is difficult to distinguish the two. Therefore, early esophageal cancer and early gastric cancer are easily missed. NBI endoscopy, also known as narrow-band imaging endoscopy, is the most advanced product in the past 10 years. The principle of NBI imaging is to filter out the broadband spectrum emitted by the endoscopic xenon lamp light source through the filter and select the narrow-band light of 415 nm and 540 nm as the illumination light, the wavelength of blue light of 415 nm is short and penetrates the mucous membrane superficially, and the absorption peak of hemoglobin to the light wave is also located around 415 nm, so it is beneficial to show the The blue light of 415 nm has a short wavelength and penetrates superficially into the mucosa. It makes the tiny lesions that are difficult to be detected under ordinary light more prominent, especially for the diagnosis of early tumors of esophagus and gastrointestinal tract, which has advantages incomparable with other gastroscopes and colonoscopes, thus improving the accuracy of diagnosis of gastrointestinal tract diseases, and is a new weapon for gastroenterologists to detect early esophageal cancer and early gastric cancer. Through NBI gastroscopy, earlier esophageal and gastric cancers can be detected, and then the cancerous mucosa can be peeled off and removed under endoscopy, which is less traumatic, faster recovery and less costly for patients. It is now performed in many large hospitals in China for the ultimate benefit of patients.