The control of mercury in flue gas is challenging, and many investigators have focused on different mercury removal technologies. The application of computational chemistry in understanding mercury removal mechanisms will help to modify and design mercury removal materials, thereby improving the efficiency of the removal of mercury in flue gas. Therefore, a review of theoretical studies on the adsorption and oxidation of mercury has been undertaken in the current study. In this contribution, the homogeneous oxidation mechanisms of Hg⁰ as well as heterogeneous interactions including adsorption of mercury species and oxidation of Hg⁰ on activated carbon, metals, metal oxides and other materials have been summarized. In addition, possible future directions of theoretical calculations on understanding the removal of mercury are outlined.