Abstract: Compared with other mercury removal methods,the removal of Hg~0 by fly ash can reduce the removal cost and realize waste treatment.At present,the mercury removal efficiency of fly ash in industrial application is low,so it is of practical significance to improve its application level through in-depth study.The effect mechanism of fly ash structure and composition （organic and inorganic） on the removal of Hg~0 was organized.From the perspective of improving mercury removal efficiency,four main methods of fly ash modification were summarized:1) Halide impregnation modification.The halides formed Br*on the surface of fly ash or reacted with the unburned carbon in fly ash to form C-Br to oxidize Hg~0.The metal cations in the modifier promoted the removal of Hg~0 by accelerating the charge transfer and reducing the reaction energy barrier.2) Mechanochemical modification.The preparation process was simple and the cost was low.After mechanical grinding,the partical size decreased,and the amorphous phase and adsorbed oxygen content increased.After grinding,the unburned carbon was fully exposed and the halogenated point increased,which accelerated the process of Hg~0 oxidation by C-Br.3)Transition metal modified magnetospheres.The transition metal modified magnetospheres were enhanced and could be recycled,and new Hg~0 oxidation sites （such as C-O Group,Cl*） were introduced on the surface of the adsorbent.4) Non-thermal plasma modification.After non-thermal plasma modification,the content of surface active plasma （such as O,Cl plasma） and functional group （C=O group and ester group） increased,which promoted the adsorption of Hg~0.The effect of complex flue gas components on mercury removal efficiency of fly ash based adsorbent was further investigated,and the mercury removal performance and applicable conditions of modified fly ash were evaluated.Based on the current research progress,is was proposed to prepare fly ash-based mercury removal agents by mechanochemical modification of fly ash with magnetic metal sulphides.