Surgery is the preferred method for treating gastric cancer and the only means to cure it radically at present. Except for huge and fixed primary lesions, extensive metastasis of intra-abdominal organs and malignant disease, the primary lesions should be removed early as long as the patient’s general condition permits. The surgical methods for early gastric cancer and middle and late gastric cancer are not the same, but the only principle is to make sure to remove the tumor cells cleanly during the surgery, and strive to remove them completely before they infiltrate diffusely or spread through blood or lymph. Patients with early stage gastric cancer should build up their confidence and do not miss the opportunity to have early surgery. There are still more surgical methods for gastric cancer. Different methods are applicable to different patients, but there are only two principles, one is radical resection and the other is to maximize the quality of life after surgery. 1.Traditional radical gastrectomy Traditional radical resection surgery is to remove the primary lesion of gastric cancer together with some tissues and their corresponding regional lymph nodes, so that no cancerous tissues are left clinically, which is called R0 resection. If there is still tumor left after surgery, it is R1 or R2 resection. R1 resection means there are tumor cells left at the edge of resection under the microscope, and R2 resection means there is still tumor not removed under the naked eye. An important part of gastric cancer surgery includes the extent of lymph node clearance, which is divided into different radical surgeries according to the extent of regional lymph node clearance: D0 surgery if the first station lymph nodes are not completely cleared; D1 surgery if the first station lymph nodes are completely cleared; and D2 or D3 surgery if all the second or third station lymph nodes are cleared. Currently, D2 lymph node dissection is advocated for progressive gastric cancer. The scope of radical major gastrectomy generally includes the upper or lower 2/3-3/4 of the stomach including the gastric tumor, all of the omentum and the tissues connecting the stomach to the surrounding organs. If the tumor invades surrounding organs such as the body or tail of the spleen and pancreas, it should be resected as completely as possible. The principle of resection generally requires 4-125px from the tumor, and for some gastric cancers with less malignant degree, the resection scope can be reduced appropriately. 2.Palliative surgery Palliative surgery includes palliative resection surgery and symptom reduction surgery. There are also different opinions on palliative resection surgery. One opinion is that palliative resection can only relieve pyloric obstruction, bleeding and pain to relieve symptoms, but not prolong life. Therefore, if the cancer is found to be incurable by dissection, the resection should be abandoned if there are no such complications. Most of the opinions believe that many patients with gastric cancer who were considered palliative resection at the time of surgery survived for more than 5 years after surgery, and even the 5-year survival rate can reach about 11%. Domestic statistics show that the survival rate of palliative resection of gastric cancer is 117%. It is generally believed that we should try to take a positive attitude towards tumor resection and never remove what can be completely removed simply so that patients lose the chance to cure the disease. For gastric cancer, the first treatment is crucial, especially surgery. If the tumor cannot be completely removed but there is a pyloric obstruction and the patient cannot eat or food cannot be absorbed, the digestive tract at both ends of the obstruction needs to be connected, which is short-circuit surgery. In some patients, even short-circuit surgery cannot be performed, or a nutrition tube can be left in the jejunum to facilitate infusion of nutrition solution. All these are within the scope of palliative or symptom improvement surgery. 3.Surgical treatment of early gastric cancer The proportion of early gastric cancer in China is generally about 10%, and the treatment effect is better, and the 5-year survival rate is more than 90%. Therefore, the surgery for early gastric cancer can be appropriately narrowed down or even surgically removed under endoscopy. In recent years, with the increasing number of early gastric cancer cases and the growing experience in surgery, more clinical data have been accumulated. The methods of endoscopic resection mainly include endoscopic mucosal resection and endoscopic submucosal dissection, which are actually simply the complete removal of the tumor of the stomach. They are based on the theory that early gastric cancer has little chance of metastasis. Operationally, the latter is relatively more complicated. Theoretically, two conditions must be met for radical endoscopic treatment of early gastric cancer: one is the absence of lymph nodes and distant metastases, and the other is the complete elimination of cancerous tissues. Since the endoscopic observation of the lesion may produce errors, if it is found that the above radical requirements cannot be met during the examination of the resected specimen, a second surgery is needed to remedy the situation. 4.Why chemotherapy is needed after radical surgery for gastric cancer In the past, it was thought that malignant tumor was only a local disease at the beginning, and then invaded to the surrounding area, firstly by lymphatic tract metastasis and finally by blood systemic metastasis, therefore, the key to treat malignant tumor is to completely remove the tumor at an early stage and strive for extensive surgery. However, in recent years, it has been recognized that after the occurrence of tumor, tumor cells are continuously shed and enter the blood circulation. Although most of them can be eliminated by the immune defense mechanism of the body, a small number of un-eliminated tumor cells will become the root cause of recurrence and metastasis, therefore, when malignant tumor is clinically detected and operated, in fact, some patients have distant metastasis. Since the recurrence and metastasis rates are high after simple surgery for progressive gastric cancer, the efficiency of many effective chemotherapeutic drugs or combination drug regimens for gastric cancer is often up to 40% or more. Therefore, it is hoped to apply postoperative adjuvant chemotherapy to deal with possible subclinical metastases after radical surgery in order to prevent recurrence and improve the efficacy. Over the past 40 years, a number of studies have been conducted in this area, with most early findings concluding that postoperative adjuvant chemotherapy is ineffective and a few studies concluding that it is effective. In recent years, more comprehensive data analysis has confirmed that postoperative chemotherapy is mildly effective, especially for patients with stage II and III gastric cancer and stage I high-risk patients who should receive chemotherapy. The possibility of postoperative survival of patients after radical resection of gastric cancer with oral tegeo for one year has now been confirmed by a large clinical study, which was conducted in Japan. Adjuvant chemotherapy is recommended for progressive gastric cancer even if radical resection is undergone.