A surface dielectric barrier discharge plasma reactor was employed to study Hg-0 oxidation in coal-fired flue gas. The experimental results showed that 98 % of Hg-0 oxidation efficiency and 13.7 mu g kJ(-1) of energy yield were obtained under a specific energy density (SED) of 7.9 J L-1. Increasing SED was beneficial for Hg-0 oxidation due to higher production of active species. Higher initial concentration resulted in lower Hg-0 oxidation efficiency, but higher amount of Hg-0 oxidation. Water vapor inhibited Hg-0 oxidation because the generation of O-3 was suppressed. The presence of NO remarkably restrained Hg-0 oxidation, while SO2 showed little effect on Hg-0 oxidation. Roles of active species in Hg-0 oxidation were examined under different gas atmospheres (O-2 and air), indicating that O-3 played an important role in Hg-0 oxidation. Deposits on the internal surface of the reactor were analyzed by energy dispersive spectroscopy and the product was identified as HgO.