The so-called tumor radiotherapy is a local treatment method that uses radiation to treat tumors. Through radiation, it destroys the DNA replication, RNA transcription and protein synthesis of cancer cells to stop the division and proliferation of cancer cells and kill or inhibit the growth of cancer cells. Chemotherapy, on the other hand, is a chemical drug treatment, which is delivered to the patient’s body through intravenous drip, intravenous injection, intramuscular injection, subcutaneous injection and oral administration, and reaches all tissues and organs of the body with blood circulation, including both the location of cancer cells and normal tissues and organs. Therefore, it is inevitable that there will be side effects as well as therapeutic effects, and the two are very different treatments. In terms of treatment scope, radiotherapy is a local treatment, while chemotherapy is a systemic treatment, and in terms of treatment tools, radiotherapy uses gas pedals to utilize radiation, while chemotherapy is a drug treatment. Radiotherapy for gastric cancer is often used as preoperative or postoperative adjuvant treatment, and palliative treatment for advanced gastric cancer. Preoperative radiotherapy for gastric cancer is indicated for patients who cannot undergo direct surgical resection because of their disease, usually patients with locally advanced or late progressive gastric cancer. Some patients can regain the chance of surgery after receiving radiotherapy, while postoperative radiotherapy is usually indicated for patients with T3, T4 or lymph node metastasis. Palliative radiotherapy usually refers to advanced treatment or local recurrence or metastasis after surgery, when the effect of treatment is poor, and palliative treatment is generally considered to maximize the survival period and the quality of life of the patient.