In this study, two models are developed to investigate the performance of a solid oxide electrolysis cell (SOEC) for CO2 electrolysis at different levels. The first model is a one-dimensional model which is basing on a previously developed electrochemical model for steam electrolysis and considered all overpotentials in the SOEC. The second model is a two-dimensional thermal-fluid model consisting of the 1D model and a computational fluid dynamics (CFD) model. It is found that the mean electrolyte temperature initially decreases with increasing operating potential, reaches the minimum at about 1.1 V and increases considerably with a further increase in potential. At the thermal-neutral voltage (1.463 V at 1173 K), the calculated mean electrolyte temperature matches the inlet gas temperature. Increasing the operating potential increases both the local current density and the electrolyte Nernst potential. The electrochemical performance can be improved by increasing the inlet gas velocity from 0.2 m s(-1) to 1.0 m s(-1) but further increasing the inlet gas velocity will not considerably enhance the SOEC performance. It is also found that a change of electrode permeability in the order of 10(-16) m(2) to 10(-13) m(2) does not noticeably influence the SOEC performance in the present study, due to negligible convection effect in the porous electrodes. (C) 2010 Elsevier B.V. All rights reserved.