Objective To develop a preventive care program for Radiotherapy-induced Oral Mucositis (RIOM) in patients with nasopharyngeal carcinoma, and to evaluate its application effect.Methods A preventive care program for RIOM in patients with nasopharyngeal carcinoma was formulated through literature review, group discussion and the Delphi technique based on the theory of "Timing It Right".Nasopharyngeal carcinoma patients undergoing radiotherapy were divided into a control group and an intervention group chronologically, with 44 patients in each group.The control group received routine nursing, while the intervention group was cared using the preventive care program for RIOM.Results Experts′ response rates were 100% in the 2 rounds of expert consultation, experts′ authority coefficient were 0.839 and 0.868 and the Kendall coefficient of concordance were 0.380 and 0.409 respectively (both P＜0.05).After the intervention, the oral mucosal condition, Body Mass Index and quality of life of the intervention group were significantly better than those of the control group (all P＜0.05).Conclusion Implementation of the preventive care program for RIOM in patients with nasopharyngeal carcinoma is conducive to improving their oral mucosal condition, nutritional status and quality of life.