Objective:To evaluate the 8 th edition of AJCC/UICC staging system for stage Ⅲ nasopharyngeal carcinoma (NPC) by the survival analysis. All patients were treated with intensity-modulated radiotherapy (IMRT). Methods:Among 1351 treatment-na?ve NPC patients who received radiotherapy/chemoradiotherapy in our hospital from December 2008 to October 2014, 742 and 784 cases were classified as clinical stage Ⅲ based on the criteria of the 7 th and 8 th edition of AJCC/UICC staging systems, respectively. These patients were classified into three subgroups according to the 7 th and 8 th edition of AJCC/UICC staging systems: T 3N 0-1 as G 1( n=226, n=245), T 1-2N 2 as G 2( n=180, n=187) and T 3N 2 as G 3( n=336, n=352). The 5-year overall survival (OS), progression-free survival (PFS), distant metastasis-free survival (DMFS) and local-regional recurrence-free survival (LRRFS) were analyzed with Kaplan- Meier method. The differences among different groups were evaluated by log-rank test. Results:There were 93.6% patients evaluated by the 8 th AJCC/UICC staging system remained the same cohort with those by the 7 th AJCC/UICC staging system. The 5-year OS, PFS, DMFS and LRRFS of the 8 th and 7 th staging systems were 84.8% and 85.4%, 76.2% and 77.0%, 80.4% and 81.3%, 89.8% and 90.6%, respectively (all P>0.05). The OS, PFS or DMFS significantly differed among three subgroups classified by the 8 th staging system (all P<0.001). In addition, statistical significance was observed between G 1 and G 2, and between G 1 and G 3(both P<0.05), whereas no statistical significance was noted between G 2 and G 3( P=0.183, 0.310, 0.248). Conclusions:The distribution features and clinical endpoints of clinical stage Ⅲ defined by the 8 th AJCC/UICC staging system are similar to those defined by the 7 th AJCC/UICC staging system. The distribution of survival risk significantly differs among different subgroups. N 2 plays a major role in assessing the survival risk of patients with stage Ⅲ NPC. In the era of IMRT plus chemotherapy, the effect of local tumors on clinical prognosis has been diminished. The 8 th AJCC/UICC staging system remains to be further improved.