Abstract: The effect of NO on the performance of Cu-Mn spinel sorbent in the removal of Hg⁰ from flue gas was investigated by using experimental and density functional theory (DFT) calculation methods. The results indicate that NO shows slightly inhibitory effect on the Hg⁰ removal on the CuMn₂O₄ sorbent at high temperature (>250 ℃), probably due to the competitive adsorption between NO and Hg⁰ on the sorbent surface. At low temperature (< 250 ℃), NO has little influence on the Hg⁰ removal. The mercury species adsorbed on the CuMn₂O₄ sorbent exist mainly in the forms of Cu-Hg amalgam and Hg(NO₃)₂. NO can be oxidized into NO₂ over the CuMn₂O₄ sorbent and NO₂ then react with adsorbed mercury to form Hg(NO₃)₂. Cu and Mn atoms are identified as the active sites for the adsorption of NO and Hg⁰. There is a strong interaction between NO and CuMn₂O₄ surface, which is closely associated with the orbital hybridization of Cu, Mn, and N atoms.