Early diagnosis and resection are the primary means of treating gastric cancer. Endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) have become one of the minimally invasive surgery modalities for early gastric cancer because of their characteristics of minimal injury, mild postoperative pain, and quick recovery and discharge. The prerequisites of radical resection for endoscopic treatment of gastric cancer include: 1) no lymph node metastasis; 2) sufficient safe margins in horizontal direction (extent of intramucosal infiltration) and vertical direction (depth of infiltration); and 3) detailed pathological histological examination of the resected specimen after surgery. 1. Indications for endoscopic treatment of intramucosal gastric cancer The infiltrative growth of early gastric cancer includes horizontal direction (superficial infiltration) and vertical direction (deep infiltration and protrusion into the gastric lumen), while superficial infiltration shows the size of the lesion, while vertical infiltration shows the depth of infiltration in the gastric wall and lymph node metastasis, which determine whether endoscopic surgery can be performed to treat early gastric cancer. The prerequisites for radical resection of endoscopic treatment of gastric cancer are no lymph node metastasis, sufficient safe margins in the horizontal direction (extent of infiltration in the mucosa) and vertical direction (depth of infiltration), and detailed pathological histological examination of the resected specimen after surgery. The specific indications for endoscopic treatment are: all differentiated intramucosal carcinoma without lymph node metastasis without ulcerative erosion, differentiated type with ulcerative erosion below 3 cm in diameter and undifferentiated intramucosal carcinoma without ulcerative erosion below 2 cm in diameter; differentiated submucosal carcinoma without ulcerative erosion below 3 cm in diameter and undifferentiated submucosal carcinoma without ulcerative erosion below 2 cm in diameter. 2. Criteria for determining complete histological resection of gastric cancer endoscopy In recent years, the Committee on Endoscopic Treatment of Gastric Cancer of the Japan Society for Gastric Cancer Research has recommended the following criteria: 1) complete resection: negative histological section, no residual cancerous tissue on additional endoscopy and biopsy; 2) relatively incomplete resection: unknown or positive histological section, no residual cancerous tissue on additional endoscopy and biopsy without further treatment; 3) absolute incomplete resection: no residual cancerous tissue on additional endoscopy and biopsy 3) Absolute incomplete resection: additional endoscopy and biopsy with cancer tissue residue. Factors reported in the literature that affect the residual cancer cells include the size and location of cancer foci; the type of cancer tissue; and the degree of diagnostic clarity of the boundaries of cancer infiltration. 3. Advantages and disadvantages of endoscopic therapy Advantages: 1) small trauma, rapid recovery of organ function after surgery, mild pain and early departure from bed; 2) surgery under closed conditions to avoid the influence of exogenous factors of open surgery; 3) treatment can be videotaped at the same time to provide visual image data for postoperative retreatment and academic exchange. Disadvantage: If postoperative pathological histological examination confirms residual cancer at the severed end or cancer infiltration depth below the submucosa layer cases, it is necessary to supplement laparoscopic surgery or surgical radical surgery again. 4.Endoscopic treatment methods of gastric intra-mucosal cancer 1）Endoscopic mucosal resection, i.e., to draw up the lesion in the shape of polyp by attraction or with forceps, and then to remove the lesion with the help of collar, EMR treatment methods include exfoliation biopsy method, endoscopic double collar polyp removal method, local injection of hypertonic solution into adrenal gland, transparent cap assisted endoscopic mucosal resection and endoscopic suction mucosal resection method. (2) Endoscopic submucosal dissection is a treatment method to remove lesions by cutting the mucosa around the lesions with knives and dissecting along the submucosal layer, which is suitable for dangerous cancer foci without lymph node metastasis in any part of the stomach and easy to operate. It includes IT knife, hook knife, Flex knife, triangle knife, needle knife, etc. ESD has the following advantages: 1) ESD can remove a wider range of lesions (>2 cm) and can perform pathological histological examination to evaluate whether there are cancer cells remaining at the cut edge, which has been applied to the treatment of early esophageal, gastric and colorectal cancer in Japan, etc.; 2) some ulcerative lesions can also be removed. Its operation time is longer and there is a risk of combined bleeding and perforation.