Radiotherapy is the treatment of tumors with rays produced by treatment machines or isotopes, it is a local treatment method and occupies an extremely important position in the treatment of tumors. At present, about 45% of malignant tumors can be cured, of which 22% are cured by surgery, 18% by radiotherapy and 5% by chemotherapy. About 60-70% of tumor patients in the United States have received radiotherapy. It mainly plays a role in the following aspects: 1. Preventing tumor recurrence: As the growth of tumor is mainly manifested as infiltrative growth like tree roots, there are often some subclinical lesions that need microscope to be found in addition to the large tumor visible to the naked eye, and these lesions are sometimes difficult to be cut out by surgery, thus becoming the root cause of recurrence. In addition, some tumor cells adhere to the surgeon’s gloves or surgical instruments during surgery and then plant on the surgical wound or incision, laying the groundwork for future recurrence. Post-operative radiotherapy can destroy these microscopic lesions and reduce future recurrence, for example, for patients with mid-stage and advanced breast and rectal cancer. 2.Radical tumor treatment: Many tumors, such as nasopharyngeal carcinoma, are not easily reached by surgery due to their location at the base of the skull and are difficult to be completely removed, plus they are more sensitive to radiotherapy, so radiotherapy can achieve the same efficacy as surgery, while avoiding the destructive nature of surgery. 3. Combined with surgery to preserve organs: At present, foreign countries have widely adopted “small surgery and large radiotherapy” to treat certain tumors in order to preserve the function of diseased organs. For example, breast cancer adopts the surgery of enlarging the tumor and preserving the breast; most patients with osteosarcoma of the limb do not need to adopt amputation but preserve the limb, and postoperative prophylactic radiotherapy. 4. Palliative treatment: It is mainly used to relieve patients’ symptoms and prolong their lives, such as local pain treatment for patients with bone metastases; brain irradiation for patients with brain metastases to relieve hemiplegia of limbs, and so on. Finally, because radiation therapy has been widely carried out in China for a relatively short period of time, coupled with the very strong professionalism, the majority of patients know less about it, and many clinical staff at the grassroots level have a lack of knowledge about it, so sometimes they cannot reasonably arrange patients’ treatment. Therefore, it is recommended that the majority of patients should see a specialist oncology clinic after surgery in order to receive timely and reasonable radiation therapy.