Abstract: By applying the Ontario Hydro Method (OHM) and the US EPA standard methods, the sampling of mercury in the flue gas before and after fabric filter (FF)/electrostatic precipitator (ESP) located at five coalfired power plants was carried out on site and various mercury speciation such as Hg0, Hg2+, and HgP in flue gas were analyzed. The solid samples, such as coal, bottom ash, and FF/ESP ash, were analyzed by DMA80 based on EPA Method 7473. According to mercury balance, the mercury speciation and its distribution in different locations downstream the flue gas were obtained. The mercury removal efficiency of coalfired power plants 1 and 2 installed FF is higher than 80% and 20%, respectively, while that of plants 3, 4, and 5 installed ESP is around 6%, 20%, and 4%, respectively. It can be concluded that the performance of mercury removal in FF is better than ESP, and then various factors have important effects on the mercury removal.