The local recurrence rate of gastric cancer after surgery was reported to be very high in the early years, as high as 70%-80%, and even with standardized D2 lymph node dissection, the local recurrence rate was about 30%. After local recurrence of gastric cancer, radiotherapy is a very important treatment tool. Since the stomach is surrounded by kidney, liver, spleen, spinal cord and small intestine, which are sensitive to radiation and easily damaged, it restricts the safe use of radiation therapy, and because of the deep location of the stomach, it is difficult to obtain a satisfactory radiation therapy dose distribution curve, and it may cause bleeding or perforation of gastric cancer and acute side effects such as nausea, vomiting, anorexia and weight loss, which cause difficulties in patient recovery after surgery. All these have limited the development of radiation therapy for gastric cancer. In order to reduce the side effects of radiotherapy and improve the efficacy of radiotherapy, simulated positioning and 3D conformal radiotherapy are generally recommended. The value of postoperative radiotherapy for gastric cancer has been confirmed by clinical studies. A study in the United States found that adjuvant radiotherapy/chemotherapy after radical gastric cancer surgery could compensate for the lack of lymph node dissection coverage. Intraoperative radiotherapy has also been developed and advocated in some centers.