Abstract: 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 2009to November 2012were 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,82and 61cases were classified under CTV1 and CTV 2, 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 CTV 1 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 than3 cm. The results provide a reference for the optimization of CTV in the radical chemoradiotherapy of ESCC.