Objective To understand the current status of malnutrition in nasopharyngeal carcinoma patients undergoing radiotherapy, and to analyze its risk factors. Methods A total of 281 nasopharyngeal carcinoma patients undergoing radiotherapy in the Radiotherapy Department of a class Ⅲ level A hospital in Nanning were selected as research subjects by employing the convenience sampling method. The current status of malnutrition was analyzed in patients. Patients were instructed to perform body composition analysis and detection 1 day before the end of radiotherapy, and general data of patients were investigated by using the questionnaire investigation, and data such as blood biochemical indices, adverse reactions to chemoradiotherapy, exercise states, anxiety, and depression were collected. The risk factors for malnutrition in nasopharyngeal carcinoma patients undergoing radiotherapy were analyzed by employing the multivariate Logistic regression model. Results The incidence rate of malnutrition was 48.75% (137/281) among 281 nasopharyngeal carcinoma patients undergoing radiotherapy. The results of multivariate Logistic regression analysis revealed that irregular exercise, low skeletal muscle mass index, severe pharyngeal injury, and anxiety were the risk factors for the occurrence of malnutrition in nasopharyngeal carcinoma patients undergoing radiotherapy (P<0.05). Conclusion The incidence rate of malnutrition in nasopharyngeal carcinoma patients undergoing radiotherapy is relatively high. Clinical medical and nursing personnel should early identify high⁃risk population of malnutrition, and perform individualized intervention for patients with different characteristics to improve current status of malnutrition in patients, and to decrease the incidence rate of malnutrition.