With the continuous development of endoscopic technology, endoscopic resection technology is also advancing with the times. EMR has been carried out for many years, ESD (endoscopic submucosal dissection) has been carried out abroad for more than ten years, and the technology is mature and standardized, but only in recent years has it emerged in China. Can early cancer be cut cleanly without endoscopic surgery? Not only non-medical doctors have doubts about this, but also even doctors who have been practicing for many years have doubts about this. It is normal for everyone to have such doubts, because of our fear and lack of knowledge about cancerous tumors, and it is natural for us to have the same doubts at the beginning. How can we dispel people’s doubts about minimally invasive treatment for early stage cancer? We have done systematic work, from the pathophysiology of cancer, domestic and foreign diagnostic and treatment standards and norms; attending relevant international and domestic conferences in China to understand the latest international progress; observing and learning; assigning special personnel to learn; animal experiments and finally clinical application. The technical operation is carried out gradually from easy to difficult. Early carcinoma refers to intra-mucosal carcinoma and carcinoma of submucosa, regardless of whether there is lymph node metastasis or not. Endoscopic treatment of only a part of them is intra-mucosal carcinoma excluding lymph node metastasis, which in Japan includes micro-infiltration of the submucosa. in 1996, after studying 1000 patients with surgical resection of intra-mucosal early gastric cancer at the National Cancer Center Hospital in Tokyo, it was suggested that the risk of lymph node metastasis in this type of early gastric cancer was so low that surgical radical surgery plus lymph node dissection was not necessary. in 2000 Gotoda et al. examined 5265 patients with early gastric cancer who underwent gastrectomy plus lymph node dissection, and only 2.3% of them developed local lymph node metastasis. In these lesions, lymph node metastasis was associated with hypofractionation, indolent sign, lymphovascular infiltration, and lesions larger than 3 cm with superficial ulceration. Lymph node metastasis was seen in 18% of patients with invasion of the submucosa. However, cases with lesions less than 3 cm with submucosal infiltration less than 500 um, histology suggestive of highly or moderately differentiated, and no lymphovascular infiltration showed no lymph node metastasis. The Japanese Society of Gastric Cancer has developed indications for ESD that include intramucosal carcinoma and microinfiltration of the submucosa (sm1). Colorectal intramucosal tumors without lymph node metastasis and submucosal infiltrations less than 1000 um in depth with very low risk of lymph node metastasis were designated as indications for ESD in Japan. The professor suggested that the absolute indications for ESD are lesions in the epithelial layer (m1) and lamina propria (m2), because they have almost no lymph node metastasis, and the myxomucosal layer (m3) and superficial submucosal layer (sm1) are relative indications, and the degree of differentiation, lymph node metastasis and lymphatic vessel infiltration need to be considered. We refer to the opinion of the pathology department, and the current mastery criteria are stricter. The depth of infiltration is mastered at m1 and m2, and additional surgery or chemotherapy will be communicated with the patient and family if the mucosal muscle layer is invaded. Pre-operative CT or ultrasound endoscopy must be performed before ESD to exclude lymph nodes except metastasis. The determination of the border is the first step of ESD. For gastric lesions, especially when combined with intestinal metaplasia, the border is more difficult to determine, we use magnification gastroscopy to magnify and observe, combined with staining, according to the different openings of the glandular ducts, we can observe the precise border of the lesion, we mark about 5 mm outside the border, and do circumferential incision outside the marked point, and the cut down specimen requires the marked point on the specimen. What is more critical is the work of the pathology department. Our resected specimens are relatively large, with a maximum length of 5 cm, and the pathology department makes sections every 3 mm, requiring multiple sections, each of which is carefully observed to find the heaviest lesions and the most deeply infiltrated areas, and to determine whether there are residuals at the edges, providing us with the most accurate pathological assessment that can be used to guide our next work. Lesions with residual disease require the most aggressive surgery or chemotherapy. The review is usually done at 1 month, 3 months, 6 months and 1 year after surgery. During the review, we use magnification endoscopy to look carefully for irregular openings of the glandular ducts and take biopsies at suspicious areas. The fear of cancer makes us work conscientiously, doing every detail and not daring to relax at every step. The strict screening of cases, careful marking of lesion boundaries, rigorous pathological evaluation, and close postoperative follow-up allow us to say with great confidence that endoscopic treatment of early cancer can indeed be completely eradicated. After doing ESD, we feel the importance of early cancer diagnosis even more, and improving the detection rate of early cancer is a higher requirement for us. Applying staining endoscopy, NBI (electronic staining) and magnifying endoscopy can enable us to detect lesions and take biopsy of suspicious lesions, which helps us to detect early cancer more often. It lays the foundation for the treatment of early cancer.