Abstract: Objective:To investigate the changes of circulating tumor cells in locally advanced esophageal squamous cell carcinoma pa-tients treated with concurrent chemoradiotherapy. The effect of these alterations on the patients ’prognosis was also analyzed. Meth-ods: Circulating tumor cells were detected by immunomagnetic enrichment and fluorescence in 48cases of locally advanced esopha -geal carcinoma patients treated with concurrent chemoradiotherapy. The dynamic changes of circulating tumor cells were compared between pre- and post-chemoradiotherapy. Moreover, the association of these changes with the clinical characteristics and two-year survival rate were analyzed. Results: The positive rate of circulating tumor cells was closely associated with the T stage, lymph node metastasis, and clinical stage (P<0. 05), and the positive rates in pre- and post-chemoradiotherapy were 52. 1% (25/48) and 20. 8% (10/ 48), respectively. The difference was statistically significant ( P<0. 05). Kaplan-Meier analysis showed that the positive rate of circulating tumor cells predicted an adverse two- year survival rate in both pre- and post- chemoradiotherapy ( P<0. 05). Cox regression analysis showed that the clinical stage and circulating tumor cells after concurrent chemoradiotherapy were independent prognostic factors in the patients with esophageal carcinoma. Conclusion: Circulating tumor cells can reflect the disease progression in patients with locally advanced esophageal cancer. These cells can also predict the prognosis of esophageal cancer patients treated with concurrent chemo -radiotherapy.