Malnutrition is a common clinical manifestation of cancer patients and one of the most common complications of radiotherapy patients. Malnutrition will adversely affect the toxicity and side effects of cancer patients and the efficacy of radiotherapy. Therefore the nutritional treatment of cancer patients receiving radiotherapy is of great significance. Based on this Chinese Society of Nutritional Oncology China Society for Radiation Oncology Radiation Oncology Physicians Branch of Chinese Medical Doctor Association experts to formulate this guideline which contents mainly based on the current Chinese nutritional treatment status of radiotherapy patients evidence published at home and abroad combined with the experience and opinions of experts in the fields of clinical pharmaceutical nutrition nursing etc. used the European Society of Cardiology ESC evidence grading and recommendation intensity standards and focused on the screening evaluation education treatment of malignant cancer receiving radiotherapy for analysis discussion and summary. Finally the clinical diagnosis and nutritional treatment guidelines for cancer patients with radiotherapy were formulated for clinicians to provide a reference basis for standardized diagnosis and treatment.