In this work, 0.15 mol/L CuCl2 solution was used to impregnate rice husk char. Experiments were conducted in a laboratory-scale fixed-bed reactor to investigate the oxidation mechanism of Hg0 by acidic gases. The effects of acid gases (SO2, HCl and NO) atmospheres on the mercury removal efficiency of the adsorbent were studied by FTIR, XPS and experiments. The FTIR results showed that the surface of the prepared rice husk char adsorbent contained a large amount of Cu2+ and chlorine-containing functional groups. The XPS results showed that the Cu+ on the surface of the adsorbent increased after mercury adsorption. This work shows that the inhibitory effect of SO2 on Hg removal is reflected in the blockage of the pore structure on the adsorbent surface; the competitive adsorption of O2 needed for the generation of C-O*, the formation of an acid mist by SO2 hinders the contact of Hg0 with the active site. The promotion of HCl is due to the production of active chlorine substances (Cl*) to promote the oxidation of Hg0 to HgCl, HgCl2 and HgO. And introduction of NO will react with O2, while generation of NO2 is beneficial to the oxidation of Hg0 to HgO and Hg(NO3)2. The optimum mercury removal efficiency of the adsorbent is nearly 100% under certain conditions.