The dominant growth planes (0 0 0 1) and (1 1 0 2) have been used to investigate the activity of the natural alpha-Fe2O3 in chemical-looping combustion system based on density functional theory (DFT) calculations. In the chemical-looping combustion system, CO is selected as the probe fuel gas to detect the activities of the different surfaces. CO interacts stronger to Fe2O3 (1 1 0 2) than Fe2O3 (0 0 0 1). CO can be oxidized into CO2 species directly on Fe2O3 (1 1 0 2) rather than Fe2O3 (0 0 0 1). The formation of CO2 accompanying with a transformation from hematite to magnetite acted as the key step for the reduction process of hematite. (C) 2011 Elsevier B.V. All rights reserved.