Three-dimensional conformal radiotherapy (3D-CRT): 3D-CRT utilizes precise stereotactic techniques, CT simulated positioning, 3D image reconstruction technology and three-dimensional computerized treatment planning (3D-TPS) modalities, conformal lead model or multileaf collimator and coplanar or non-coplanar multifield stereotactic irradiation techniques to make the distribution of isodose curves consistent or basically consistent with the shape of the target area; the aim is to reduce the irradiation dose to normal tissues, maximize the irradiation dose to the tumor area, reduce complications and improve the local control rate. MLC-supported three-dimensional conformal radiotherapy (3D-CRT) is a new radiotherapy technique that can make the distribution of high-dose areas in the three-dimensional direction (i.e., in the three-dimensional direction) consistent with the shape of the tumor target area; the application and development of stereotactic conformal radiotherapy is the inevitable trend of modern tumor radiotherapy technology. The application and development of stereotactic conformal radiotherapy is the inevitable trend of modern tumor radiotherapy technology to achieve the four principles of radiotherapy. Currently, three-dimensional conformal radiotherapy (3D-CRT) is widely used in the treatment of various types of tumors throughout the body, and when used together with conventional radiotherapy, its therapeutic efficacy and side effects are better than those of conventional radiotherapy alone, and it has become the most important technical means in the field of clinical radiation therapy for tumors.