In conventional radiotherapy, the normal tissues or organs are irradiated in a larger area and receive more radiation dose, resulting in serious complications, leading to serious organ damage and functional impairment, causing great pain to patients and poor quality of life after healing; if the irradiated area is reduced, some tumors may not receive sufficient dose locally, leading to local control failure and thus causing tumor recurrence. The concept of conformal radiotherapy and clinical research first started in 1959, when Dr. Takahash and his colleagues in Japan first proposed and clarified the basic concept of conformal radiotherapy and the method of its implementation. The basic goal of radiation therapy is to maximize the radiation dose to the lesion (target area) and kill the tumor cells, while leaving the surrounding normal tissues and organs with little or no unnecessary exposure. However, since the difference between the lethal dose of tumor and the tolerated amount of normal tissues is not very large, some important organs such as brainstem, spinal cord, kidney, gonads, etc. or close to the tumor (target area) should be protected with care during the radiotherapy treatment of tumor. Therefore, the ideal radiation therapy technique should give a high lethal dose to the target area according to the shape of the tumor, while the normal tissues around the target area are not irradiated, in the direction of irradiation, an object has different shapes from different angles, and the size of the tumor also has different shapes from different angles. Conformal radiation therapy is a technique in which the shape of the irradiation field is consistent with the shape of the tumor (target area), that is, the shape of the high-dose area distribution is consistent with the shape of the tumor (target area) in the three-dimensional direction. The whole process of conformal radiotherapy includes four stages: spatial localization of the lesion (target area) and important organs and tissues, treatment plan design, confirmation of the treatment plan, and implementation of the treatment plan. There are two prerequisites for the implementation of conformal radiotherapy: (1) the spatial localization of the lesion (target area) and important organs and tissues, the radiotherapist must know accurately the three-dimensional information of the lesion (target area) and important organs and tissues through CT, MRI, PET and other advanced imaging tools, in order to give a high lethal dose to the tumor without irradiating the normal tissues around the tumor (target area); (2) the patient should keep the treatment plan intact during each treatment. During each treatment, keep the consistency of treatment position, such as doing body membrane, pleura, cephalic membrane fixation and stereotactic frame, vacuum pad and other methods of fixing patient’s position. ③Physicians do the planning. The form of conformal radiotherapy is realized, such as multi-leaf collimator (MLC), which generally consists of 20?120 pairs of blades, can guarantee its shape is consistent with the shape of the target area (tumor); the mold chamber can make conformal block, which is generally made of low melting point lead (LML), and can be made into a specific arbitrary shape block. Results of conformal radiation therapy: Since the shape of the irradiation is consistent with the tumor, the irradiation dose to the tumor (target area) is further increased, which improves the unnecessary irradiation to the surrounding normal tissues and organs and reduces the complications, which is confirmed in the clinical practice of conformal radiation therapy for nasopharyngeal cancer, prostate cancer, lung cancer and intracranial tumors. As the dose to the tumor (target area) is improved, it will inevitably lead to an increase in the local control rate of the tumor; the improved local control rate of the tumor will inevitably reduce the distant metastasis rate, which in turn improves and increases the survival rate. Conformal radiation therapy is particularly suitable for the treatment of tumors with complex anatomy (e.g. intracranial and cephalic), special shape and multiple targets, which can reduce radiation complications and improve the quality of patient survival. Since the dose of surrounding normal tissues and organs is further reduced after using conformal radiation therapy, it is possible to learn from the experience of stereotactic therapy, change the traditional dose fractionation pattern, increase the fractionated dose and reduce the number of treatment fractions to shorten the treatment course, which will be more beneficial to the tumor control.