Objective:To explore the effect of clinical target volume (CTV) optimization on long-term survival and late xerostomia of patients with nasopharyngeal carcinoma (NPC).Methods:Clinical data of 763 patients with NPC treated with intensity-modulated radiotherapy (IMRT) in the Jiangsu Cancer Hospital from January 2015 to November 2018 were retrospectively analyzed. All patients were divided into the modified and conventional CTV groups. Propensity score matching (PSM) was applied to balance the distribution of baseline features. The degree of xerostomia was evaluated by Radiation Therapy Oncology Group (RTOG) / European Organisation for Research and Treatment of Cancer (EORTC) standard and Jiangsu Cancer Hospital Multi-dimensional Radiotherapy-Induced Xerostomia scale. Survival analysis was performed by Kaplan-Meier method. The difference of xerostomia between two groups was compared by rank-sum test. The dose parameters of salivary glands were compared by independent sample t-test. Prognostic factors of survival and xerostomia were assessed by univariate / multivariate regression analyses. Results:There were no significant differences in overall survival, local recurrence-free survival, distant metastasis-free survival and progression-free survival between conventional and modified CTV groups before and after PSM. There were no significant differences in the incidence of late xerostomia above grade 2 of RTOG/EORTC standard between two groups. Using multi-dimensional scale criteria, NPC patients in the modified CTV group developed less late xerostomia than those in the conventional CTV group ( P<0.05). D mean and V 26 Gy of bilateral parotid glands, D mean and V 39 Gy of bilateral submandibular glands, and D mean of sublingual glands and mouths were reduced after optimization of CTV (all P<0.001). Univariate analysis showed that clinical staging, T staging and N staging were the independent prognostic factors of overall survival. Multivariate analysis demonstrated that clinical staging was the independent prognostic factor of overall survival. The risk factor for xerostomia during night sleep was the D mean of sublingual glands. Conclusion:The optimization of CTV in IIb region in NPC treated with IMRT can better protect salivary glands and reduce the incidence of late radiation-induced xerostomia on the premise of ensuring long-term survival.