First of all, it is the positioning aspect, because the tumor is affected by body position, breathing and other factors, the position is difficult to be fixed, ordinary radiotherapy is positioned by simulation positioning machine, and the treatment range is marked on the patient’s skin with skin ink. Precision radiotherapy solves the problem of body position fixation very well by using three-dimensional stereotactic body frame, body model and vacuum pad, letting the patient lie flat on the three-dimensional conformal treatment bed, then fixing the patient with the body model, and positioning the patient on the spiral CT, which not only fixes the tumor adequately, but also carries out the precise three-dimensional stereotactic positioning, so as to ensure that all the rays are concentrated on the tumor and reduce the error, avoiding the radiation from the tumor, and avoiding the error of positioning. This not only can fully fix the tumor, but also carry out precise three-dimensional orientation positioning, so as to ensure that all the rays are focused on the tumor to the maximum extent, reduce the error and avoid the damage of the rays on normal tissues. Secondly, in terms of treatment, ordinary radiotherapy treats tumors from a single plane. When treating a tumor in one plane, the dose of radiation cannot reach the lethal dose of the tumor at once, so as to make it die completely. Because the tumor is surrounded by normal tissues, if the dose of radiation reaches the lethal dose when treating the tumor in a single plane, it will certainly kill the normal tissues surrounding the tumor. Therefore, ordinary radiotherapy must relatively expand the scope of illumination when treating tumors, and the patient’s reaction to illumination is more obvious. On the other hand, three-dimensional conformal radiotherapy is a kind of three-dimensional treatment, which can set 3~6 points according to the three-dimensional shape of the tumor to carry out an all-round “attack” on the tumor tissue. Although the dose of one point is very small, the cumulative dose of multiple points can easily reach the lethal dose of the tumor, thus it can easily achieve the purpose of tumor treatment, and the damage to normal tissues is tiny, and the patient’s response to radiotherapy is obviously reduced, and the treatment effect is obviously improved compared with ordinary radiotherapy. The process of intensity-modulated conformal radiotherapy is extremely complicated, which not only requires precise positioning system, advanced treatment planning system and radiotherapy equipment, as well as strict quality control and validation system, but also requires close cooperation of a group of radiotherapists, physicists and technicians with high technical quality, so that only larger tumor radiotherapy centers can really achieve precise radiotherapy.