Abstract: In this study, in order to improve the mercury removal performance of Mn-Co-Fe spinel adsorbent, KX (X represents Cl, Br and Ⅰ) modified Mn-Co-Fe spinel adsorbent is prepared by using sol-gel self-combustion method and impregnation method at first. Then, the surface morphology, the proportion and distribution of surface elements, the specific surface area and total pore volume, the crystal phase structure and the specific saturation magnetization characteristics are characterized by SEM, SEM combined with EDS energy spectrum mapping, BET, XRD and VSM, respectively. The effects of potassium halide type, potassium halide loading, adsorption reaction temperature and initial mercury concentration on mercury removal performance in simulated coal-fired flue gas are investigated through a fixed bed. Finally, the control mechanism of mercury removal by adsorbent and the present valence state of mercury on the adsorbent surface are studied based on dynamic simulation, XPS characterization and temperature programmed desorption experiment. The results show that under the same experimental conditions, the average mercury removal efficiency of 0.10KX@MCFS is KI (92.84%) > KBr (88.39%) > KCl (86.61%). Additionally, with the increase of the KI loading, adsorption temperature and inlet mercury concentration, the mercury removal performance of modified MCFS can be improved to a certain extent. Although the loading of KI leads to the decrease of the magnetic properties of MCFS, the comprehensive analysis shows that 0.10KI@MCFS has a relatively excellent mercury removal performance and saturation magnetization (34.0 emu/g). Therefore, the findings of this study have an important reference value for the practice of mercury pollution emission control and magnetic recovery of adsorbents.