The ideal radiation therapy would be to give only a very high dose to the tumor, maximizing the killing of the tumor, while the normal tissue receives the smallest dose of radiation. This sounds like a luxury. Three-dimensional conformal radiation therapy is a new radiotherapy technique to achieve this ideal. Three-dimensional conformal radiation therapy is the distribution of high-dose areas in a three-dimensional direction (i.e., in a three-dimensional orientation) that corresponds to the shape of the target area. The tumor target area is given a very high dose according to the shape of the tumor, so that the tumor cells are killed and the tumor is treated; while the normal tissues around the tumor target area are irradiated with little or minimal dose. This technique makes it possible to give high radiation doses to tumors even when the normal tissues next to the tumor are poorly tolerant to radiation. Virtually all tumors do not have a regular shape. We control the shape of the irradiation field from the three-dimensional direction according to the three-dimensional situation of the tumor, and develop a precise and optimized radiation treatment plan so that the radiation dose distribution matches the shape of the tumor. The optimization and implementation of this radiation treatment plan is done by the radiation treatment planning system, and the treatment plan is transmitted to the high-energy linear gas pedal, and the accuracy of the radiation field is verified by imaging to ensure precise three-dimensional conformal radiotherapy to the tumor tissue. Therefore, 3D conformal radiotherapy is a kind of precise radiotherapy that cannot be compared with other treatment methods. 3D conformal radiotherapy uses a variety of individualized body fixation techniques, which can precisely localize the tumor and ensure the precise repetition of fractionated treatment positions, thus focusing most of the radiation on the tumor target area and avoiding damage to the normal tissues around the tumor target area. Three-dimensional conformal radiation therapy is suitable for almost all tumor patients who need radiotherapy. It is especially suitable for tumors that are adjacent to important tissues and organs that need to be protected. It can also be used to compensate for smaller residual lesions after general radiotherapy. Since this technology has less damage to the adjacent tissues and can increase the dose in the tumor area, 3D conformal radiotherapy can increase the dose of local lesions to above the radical dose and increase the chance of radiotherapy to cure local tumors.