Objective:To compare the therapeutic effects by different longitude margins of the gross tumor volume (GTV) based on elec-tive nodal irradiation (ENI) and to investigate the optimization of clinical tumor volume (CTV) in the radical chemoradiotherapy of esophageal squamous cell carcinoma (ESCC). Methods:ESCC patients treated with chemoradiotherapy for the first time in the First Af-filiated Hospital of Xiamen University from May 2009 to November 2012 were retrospectively studied. All patients were treated with ENI for radical radiotherapy, and the patients were divided into two groups:CTV1 group (with longitudinal external expansion length of less than 3 cm) and CTV2 group (with longitudinal external expansion length of more than 3 cm). The survival time and occurrence of side effects in patients were compared. Results:Among the 142 cases of patients, 82 and 61 cases were classified under CTV1 and CTV2, respectively. No significant difference in the overall survival (OS) and local recurrence-free survival (LRFS) rates was observed af-ter 1, 3, and 5 years of treatment between the two groups. The occurrence of side effects, such as bone marrow suppression, radiation pneumonitis, radiation esophagitis, and esophageal fistula, was less than 5%in both groups, and the data show that the side effect oc-currence in CTV1 was significantly lower. Conclusion:In the radical chemoradiotherapy of esophageal cancer using ENI, the OS rate of patients with a delineated CTV according to a 3 cm GTV longitudinal external expansion length is not lower than that of patients with a delineated CTV according to a GTV longitudinal external expansion length of more than 3 cm. The results provide a reference for the optimization of CTV in the radical chemoradiotherapy of ESCC.