Objective To evaluate the correlation between nutritional status and radiation – induced oral mucositis ROM in nasopharyngeal carcinoma NPC patients during radiotherapy so as to provide a reference for clinical improvement of radiotherapy effect reduction of radiotherapy complication and improvement of nutrition supply. Method A total of 154 patients with NPC diagnosis for the first time into our hospital from May 2020 to May 2022 were enrolled retrospectively. They received intensity modulated radiation therapy IMRT or chemoradiotherapy for at least 4 weeks. Compare the nutritional indicators before and 4 weeks after radiotherapy including body weight body mass index BMI hemoglobin albumin and prealbumin levels and the nutritional risk screening score 2002 NRS 2002 score. After radiotherapy grade of ROM severity according to the American Common Adverse Reaction Terminology Assessment Standard CTCAE Version 5. 0 that is no mild to moderate and severe groups. Compare the nutritional indicators and nutritional intervention methods during the ROM groups. Result The body weight BMI albumin and prealbumin of 154 patients decreased significantly after radiotherapy while the NRS 2002 score increased significantly P< 0. 05 . After radiotherapy there were 41 cases in the non ROM group 91 cases in the mild to moderate group and 22 cases in the severe group. There were no differences among the three groups of all the nutritional indicators before radiotherapy P > 0. 05 . After radiotherapy the weight BMI hemoglobin albumin and prealbumin in the severe group were significantly lower than those in the mild to moderate group and the reduction of each indicator was significantly higher than that in the mild to moderate group the NRS 2002 score and increasement were significantly higher than those in the mild to moderate group too P<0. 05 there were also differences between the mild to moderate group and the non ROM group P<0. 05 . In severe group enteral nutrition was significantly more than that in mild to moderate group the time of parenteral nutrition supply was significantly longer and the total energy of nutrition supply was significantly higher there were also differences between the mild to moderate group and the non ROM group too P<0. 05 . Conclusion ROM occurrence is closely related to nutritional status which can influence and interact with each other in NPC patients during IMRT improving radiotherapy technology and reducing the risk of ROM are important method to improve nutritional status.