Radiation therapy has a history of nearly 100 years now. As early as the discovery of radium by Madame Curie and X-rays by Roentgen, radiation was quickly used in the treatment of malignant tumors. In the 1920s and 1930s, due to the availability of reliable X-ray equipment, radiophysics and radiobiology research had an important development; in the 1940s, artificial radioisotopes were manufactured; in the 1950s, 60-cobalt therapy machines began to be used in clinical treatment, and the efficacy of radiotherapy began to improve significantly; after the 1960s, various types of medical gas pedals were produced, and high-energy X-rays and electron beams were used to treat tumors and gradually replaced the ordinary X-ray machines and 60-cobalt therapy machines. After the 1960s, various kinds of medical accelerators were produced, which used high-energy X-ray and electronic wire to treat tumors and gradually replaced ordinary X-ray machines and 60-cobalt therapy machines. In some developed countries and regions, fast neutrons, protons, negative mesons and heavy particles have also been experimented and gradually applied in clinics. At present, malignant tumors have become the common and frequent diseases in the world, the incidence rate increases year by year, and its mortality rate accounts for the first or second place of various causes of death. Radiotherapy has become one of the main means in the treatment of malignant tumors, and more than 70% of patients with tumors need radiotherapy (including comprehensive treatment and individual treatment). Some malignant tumors can be cured with radiotherapy alone. Moreover, radiotherapy has become a specialized discipline called tumor radiotherapy, including clinical radiophysics, clinical radiobiology and clinical radiotherapy, and has developed rapidly over the past 40 years. Some early malignant tumors have high cure rate with radiotherapy alone, such as early nasopharyngeal cancer, cervical cancer, vocal cord cancer, Hodgkin’s lymphoma, skin cancer and so on. The 5-year survival rate of early esophageal cancer, prostate cancer, tongue cancer, etc. are similar to that of surgery, while the functional cosmetic preservation is more satisfactory. Generally speaking, 70%~80% of the tumor patients come to the hospital for consultation, and most of them cannot be operated, or have difficulty in resection, or have contraindications to operation, or are unwilling to operate, most of them need to be treated with radiotherapy, and many of them have better therapeutic effect. Radiotherapy also occupies an important position in the comprehensive treatment of tumors, such as preoperative, intraoperative and postoperative radiotherapy with surgery; radiotherapy before, during and after chemotherapy with chemotherapy; and radiotherapy, surgery and chemotherapy with integrated treatment. In conclusion, radiotherapy is an important and indispensable treatment for most malignant tumor patients, and malignant tumor patients should pay attention to the radiotherapy department for consultation and treatment.