Natural mineral (MgO) is considered to be an excellent support for loading MnOx to remove Hg0 from coal-fired flue gas. However, the restricted specific surface area of MgO limits its utilization efficiency for Mn species, and the amount of Mn species is always quite high. In order to improve the utilization of Mn active species by MgO support in the reaction of removing Hg0 from flue gas, MnOx sorbents supported by MgO-Al2O3 composite oxides were synthesized by partially replacing MgO with Al2O3. With the aid of the large specific surface area and the high proportion of chemically adsorbed oxygen (Oad) on the surface of Al2O3, the adsorption and oxidation capacity of Mn species for Hg0 was improved, and a sorbent with higher Hg0 removal efficiency was obtained. The activity test results show that when only 5% Mn species is loaded, adding 30% Al2O3 into the support can improve the Hg0 removal efficiency by 27.7% compared with the sorbent without Al2O3 in the N2+10% O2 atmosphere at 150 ℃. The mechanism of the sorbent for Hg0 removal was revealed by H2-TPR and XPS. H2-TPR shows that Al2O3 will interact with MgO to form a more stable carrier species after the addition of Al2O3. XPS shows that the proportion of Mn4+ species on the sorbent surface has an important influence on the Hg0 removal activity. When adding 30% Al2O3, the proportion of Mn4+ species on the sorbent surface is the highest, so the Hg0 removal activity is the highest. In view of the limitation of Mn active components by MgO support, the method of adding Al2O3 can improve the utilization of the active species, which has a guiding significance for the application of natural mineral support in the field of Hg0 removal.