Radiotherapy is one of the most common treatments of cancer that are used alone or with the combination of other treatments. Radiotherapy are used before surgery for tumor shrinking, pain relief, wound healing or prevention of continues bleedings. In this paper, types of radiotherapy and safety principles for nurses are considered. There are three basic methods for radiotherapy: teletherapy, brachytherapy and use of beam in the forms of solution. Teletherapy is most current form of radiotherapy and include the use of high energy of X beam, gamma beams from cobalt units and low energy of X beam.