Radiotherapy is one of the main methods of cancer treatment, as a localized treatment, the mechanism is to kill the cancer cells by radiation. There are many toxic side effects, which are divided into systemic and localized. Systemic will cause leukopenia, weakness and discomfort. Localized treatment will cause damage to local normal tissues, important organs, such as spinal cord, will cause spinal cord damage; brain radiotherapy will inevitably cause damage to normal brain tissues; head and neck tumors, such as nasopharyngeal carcinoma and laryngopharyngeal carcinoma, will cause damage to parotid glands as well as dysfunction of the oral cavity and mucous membrane damage in the process of radiotherapy, which will bring pain to the patients. In the process of treatment, the damage can be controlled within the normal range, and there is no need to worry too much.