A novel gaseous elemental mercury (Hg0) removal agent was successfully synthesized via impregnation method, by using molybdenum trioxide (MoO3) as the active component and carbon aerogel (CA) as the carrier. The as-prepared samples maintained a large specific surface area and excellent pore structure of the pure carbon aerogel, so that MoO3 was better dispersed to obtain enhanced Hg0 removal performance. The maximum efficiency of elemental mercury removal was about 74%, achieved by Mo/C500 sample at 300 oC, while it still had good ability (nearly 60%) in the range of 500-700 oC. The mechanism of mercury oxidation removal was also verified by DFT calculation. This work should help in developing suitable materials for thermocatalytic oxidation of elemental mercury, and also provide some theoretical basis and data support for full-scale application of heavy metal mercury pollution control in coalfired power plants.