”The basic principle of radiotherapy is to kill tumor cells by using the ionizing radiation effect of rays. Radiation therapy is mainly used to treat malignant tumors and is called radiation oncology. It, together with surgery and chemotherapy, constitutes the three main means of tumor treatment. Currently, about 45% of malignant tumors can be cured, of which 22% are cured by surgery, 18% are cured by radiotherapy, and 5% are cured by chemotherapy. Although patients receiving radiotherapy are mostly in the middle and late stages, their efficacy is similar to that of surgery. About 65-75% of tumor patients need radiotherapy at different times and for different purposes. In addition, radiotherapy has unique efficacy for many benign diseases that are difficult to treat with drugs or surgery. With the epoch-making development of radiotherapy equipment and the wide application of precise radiotherapy technology, the indications for radiotherapy have been gradually relaxed, the efficacy has been significantly improved, and the radiation damage has been significantly reduced. In addition, radiotherapy has the advantages of non-invasive and painless to ensure the function of five senses, such as pronunciation, swallowing, excretion and maintaining the aesthetic appearance of the body. With the rapid development of medical equipment and technology, the efficacy of radiotherapy is increasing. It has been clinically proven that radiotherapy is as effective as surgery in the treatment of early head and neck tumors, lung cancer and esophageal cancer. With high precision, low pain and reliable efficacy, radiotherapy has an irreplaceable role in cancer treatment and is becoming increasingly important.