The elemental mercury (Hg-0) capture of potassium permanganate (KMnO4)-modified calcium-based with rice husk ash sorbent (CaO/RHA) was first tested to evaluate the effectiveness of Hg-0 adsorption. The KMnO4 modified CaO/RHA performances were compared with that of modified Ca-based with fly ash sorbent (CaO/FA). The effects of supports, pore size distribution, oxidants loading, temperature, and gas mixture were also investigated to understand the mechanism in capturing Hg-0. The CaO/RHA/KMnO4 sorbent could remove over 90% of Hg-0 under the simulated flue gas.