The so-called precision radiotherapy, mainly refers to the three-dimensional modulated intensity radiotherapy, which is a tumor treatment method combining radiotherapy medicine with computer network technology and physics, etc. The whole radiotherapy process is controlled by computer. The difference with traditional radiotherapy technology can be summarized as “four most”, i.e., the largest dose in the target area (lesion area), the smallest amount of normal tissue around the target area, the most uniform dose distribution in the target area, and the most accurate target area positioning and irradiation, with the advantages of “high precision, high dose, high efficacy and low damage”. “It mainly includes 3D conformal radiotherapy and intensity modulated conformal radiotherapy. Precision radiotherapy is a new tumor radiotherapy technology based on conventional radiotherapy through precise tumor localization, precise plan design, dose calculation and precise execution on the treatment machine, which integrates 3D image processing technology, high-precision dose calculation algorithm, cutting-edge linear gas pedal series technology, advanced tumor diagnosis technology, and cutting-edge research results in radiobiology. In the whole process of precise radiotherapy, every step emphasizes precision, which is a qualitative leap compared with conventional radiotherapy. Three-dimensional conformal radiotherapy is a technique to make the shape of dose distribution in the high-dose area consistent with the shape of the target area in three-dimensional direction, as a result, the suitability of the three-dimensional shape of the high-dose distribution area and the target area is greatly improved compared with conventional treatment, and the irradiated range of surrounding normal tissues and organs is further reduced. Since most of the tumors are infiltrative in growth and their general shape is irregular, treatment with this technique can further increase the dose of tumor irradiation and reduce the amount of surrounding normal tissues, thus increasing the local control rate and survival rate, as well as reducing radiation complications and improving the quality of life of patients. However, in some cases, 3D conformal radiotherapy cannot fully achieve the purpose of treating tumors and protecting normal tissues. For example, there are more important organs or normal tissues around the tumor to be irradiated; the tumor and normal tissues or important organs are interlaced; tumor tissues encircle important organs, etc. In this case, the target area shape is either “hollow”, “horseshoe” or “crab foot”. In this case, the target area shape is either “hollow”, “horseshoe” or “crab foot”, and it is difficult to form these special irradiation target area shapes with ordinary 3D conformal radiotherapy. The result is that while the tumor is lethally irradiated, the surrounding normal tissues are protected to the maximum extent, thus reducing the radiation therapy reaction and improving the treatment effect. The result is to protect the surrounding normal tissues to the maximum extent while the tumor is lethally irradiated, thus reducing the reaction of radiotherapy and improving the treatment effect. For example, in a lung cancer patient, the tumor grows close to the spine, if irradiated by conventional techniques, the treatment is definitely palliative, which is also commonly called “not curable”, because the radiation tolerance of the spinal cord is much lower than the radical dose of the tumor. “If the spinal cord is avoided, the tumor will be palliated, which is irreconcilable. In this case, the intensity modulated conformal radiotherapy can play the role of both treating the tumor and protecting the spinal cord, which is of great significance. Another example is that after maxillary sinus cancer infiltrates the orbit and eye, intensity modulated conformal radiotherapy can play the role of protecting the crystal to treat the tumor, and then there are important organs such as kidney, spinal cord and small intestine around the retroperitoneal tumor. Therefore, many experts and scholars at home and abroad call intensity-modulated conformal radiotherapy a revolution in the history of radiotherapy treatment, which is applicable to the radiotherapy of most tumors such as prostate cancer, lung cancer, head and neck tumors, mesothelioma, central nervous system tumors, etc. It can not only enable patients to obtain a better cure rate of tumors, but also enable patients to obtain a higher quality of survival, which is the mainstream of tumor radiotherapy in the 21st century.