Endoscopic submucosal dissection (ESD) is a new method of endoscopic treatment of early mucosal lesions in the gastrointestinal tract that has emerged in China in recent years. It originated from Japanese scholars more than 10 years ago as a method to treat gastrointestinal lesions. The gastrointestinal lesions mentioned here are those that can be reached by our endoscopy. Esophagus, cardia, stomach, duodenum, large intestine (cecum, colon, rectum). The nature of lesions: precancerous lesions, which used to be called severe hyperplasia, are now called high-grade neoplasia, while early mucosal cancer is also included in high-grade neoplasia. The advantages are: firstly, the integrity of the original organs is preserved and the physiological functions remain; secondly, the lesions are completely removed, with the same effect as traditional surgery; thirdly, the large trauma of traditional surgery is avoided. Fourthly, the body recovers quickly. The fifth complication is less and smaller. Disadvantages: It requires more than ten years of operating experience of endoscopist, which is difficult and technically demanding, equivalent to the medium and major surgery level of traditional hand grading. Secondly, medical consumables are all high-value consumables, and many of them are not covered by medical insurance. Since 2010, our endoscopy room has been the first to carry out ESD in the province, and has accumulated rich experience so far, and we are able to cope with various complicated situations encountered during the operation. Of course, every work has its indications, and choosing the right method is the guarantee of restoring health and the first priority. Some scholars engaged in circumferential resection of esophageal and colonic mucosa in previous years, and I thought it was inappropriate when I started to watch their operation demonstration, because once the circumferential absence of the gastrointestinal mucosa is bound to cause stenosis, which is only 3-4 mm in diameter in severe cases, because it is a tubular mucosal absence, even with expansion balloons and other methods cannot restore normal, and the scholars who did circumferential resection also stopped the experimental operation and admitted that it is not feasible. Therefore, some scholars have recently proposed to limit the extent of mucosal resection to 2/3 of the circumference of the lumen, and I agree with this proposal. When there are multiple primary early esophageal lesions, there is a new treatment method, photodynamic. This will be described later in Photodynamic therapy for GI cancer.