A molybdenum (Mo)-incorporated magnetic Fe-Mn sorbent (Fe-Mn-Mo) was developed to capture elemental mercury from flue gas. The effect of Mo incorporation on the mercury capture performance and physicochemical properties of the Fe Mn sorbent was investigated. The mechanism for the functions of Mo on enhancing mercury capture activity was deeply studied. The fixed-bed test results display that a small amount of Mo incorporation (Mo/Mn = 0.1) improves mercury capture performance, but excessive Mo plays an opposite role. The developed Fe-Mn-Mo-0.1 sorbent can keep good mercury capture activity at relatively low temperature as well as under the atmosphere without 02 existence. The sorbent characterization result shows that the developed Fe Mn Mo-0.1 sorbent exhibits a good magnetization property, which makes it feasible to be separated from fly ash with addition of an external magnetic field. Mo incorporation (Mo/Mn = 0.1) slightly increases the Brunauer-Emmett-Teller area and reduces the agglomeration and crystallization degree of Fe Mn particles. Mo incorporation is in the form of Mo6+, which promotes the generation of more high-activity Mn4+ and lattice oxygen and increases the total oxygen storage of the Fe Mn sorbent. Mo incorporation does not change the mechanism of mercury capture, and the mercury capture process can be described by the Mars-Maessen mechanism with the adsorption product of mercurous oxide.