The staging of gastric cancer is according to TNM criteria, that is, infiltration depth, lymphatic metastasis and distal organ invasion. 1.T refers to the infiltration depth of the tumor, if it is limited to the mucous layer or submucous layer, it belongs to T1; if the infiltration depth has exceeded the submucous layer but has not broken through the muscular layer, it belongs to T2; if it is in the middle of the muscular layer and subplasma layer, it belongs to T3; if it has formed invasion to the plasma membrane and the surrounding tissues, it belongs to T4. 2.N, referring to lymphatic metastasis, is divided into three cases. No lymphatic metastasis is N0; 1-2 lymphatic metastases are N1; 3-6 lymphatic metastases are N2; more than 7 lymphatic metastases are N3. 3.M, M0 means no distal organ invasion; M1 means distal organ invasion.