CeO2 modified V2O5/AC catalysts (V-Ce/AC) were synthesized by an ultrasound-assisted impregnation method, and were employed to remove elemental mercury (Hg-0) from simulated coal combustion flue gas at low temperature (100-200 degrees C). The effects of several operation conditions, including the loading of CeO2, reaction temperature, the role of O-2 and stability of the catalysts were all investigated, respectively. The results showed that 1 V-8Ce/AC catalysts had the highest catalytic activity with 98.3% Hg-0 removal efficiency at 150 degrees C. There was synergistic effect on Hg-0 oxidation when V2O5 and CeO2 combined. Characterization by XPS, we found that both lattice oxygen (O-alpha) and chemisorption oxygen (O-beta) contribute to Hg-0 oxidation. Besides, the possible mechanism of Hg-0 removal over the catalysts was proposed, in which the critical steps were the adsorption of Hg-0 and the oxidation of Hg-0 to Hg2+ by the active oxygen on catalysts surface.