Volumetric-modulated arc therapy (VMAT), as novel technology not only can produce similar or better dose distributions, but also can reduce treatment time and the monitor units (MU). However, VMAT can only be implemented on the new generation accelerators such as the Varian RapidArc and Elekta Synergy, which prevents most existing linacs from delivering in VMAT. The purpose of this study is to investigate using constant dose rate IMAT on conventional linear accelrator, by comparing with the IMRT technology to evaluate the performance of IMAT on thoracic esophageal carcinoma patients and then provide guidance for clinical treatment. The results show that thoracic esophageal carcinoma can be implemented IMAT plans on conventional Varian 23EX Linac for smoothly and quickly at busy cancer center. Comparing with the IMRT techonology IMAT plans can meet the clinical demand, gives comparable OAR and improved CI of PTV, can reduce treatment time and high dose irradiated volume; while increase the treatment MU and low dose irradiated volume of healthy tissues and the volume of the lung V5 and V10. This point needs to pay attention to implementation in clinical.