Efficient and effective control of airborne Hg-0 emission during fossil fuels utilization is one of many challenges. The catalytic oxidation of Hg-0 to Hg2+ is a promising approach for mercury removal as it enables mercury capture at existing air pollution control devices. In this study, IrO2 was studied in detail based on density functional theory to show the interactions between Hg-0 and O-2 on the IrO2 (110) surface. On the basis of the full optimizations of the IrO2 (110) surface, five stable Hg adsorption configurations have been identified, among which the most stable adsorption position was found to be at the top of a 5-fold coordinated Ir atom (Ircus-top). Furthermore, in-depth analysis of the interactions between the Hg atom and 0 atom on the IrO2 (110) surface showed that the adsorption energy of O is higher than that of Hg-0 on the Ircus-top. Moreover, the results suggest that the preadsorption of O atoms has a positive effect on the adoption of Hg, while the adsorption was identified as a chemisorption. More importantly, the Langmuir-Hinshelwood mechanism was determined to be the most probable reaction mechanism. This study provides insight into the prediction of the potential Hg-0 catalytic oxidation by O-2 on the IrO2 (110) surface.