The basic principle of radiotherapy for cancer patients is to establish a course of therapy which offers good prospects for a cure, has tolerable adverse effects, and promises a comfortable life for the patient thereafter. There have been two paths in the development of radiotherapy. One is physical, in which efforts have been made to improve the dose concentration on the tumor while avoiding healthy tissue, and the order is biological efforts to increase radiation susceptibility of tumors. Recently, computer medicine has improved radiation planning and made high quality radiotherapy possible. Elderly patients with cancer need to be treated with minimally invasive organ-preserving therapy techniques. Radiotherapy is an important tool for cancer treatment in the past, present and future.