Abstract: For better understanding the effect of activated carbon on mercury emission in the flue gas of coal-fired power plant, mercury removal from flue gas was studied in the laboratory scale and the ultra-low emission power plant. The effects of temperature and residence time on the mercury captured using activated carbon were investigated. Results from a laboratory scale fixed bed reactor indicated that the optimal mercury captured temperature is 120℃. Activated carbon injection and mercury removal experiments were carried out in 300 MW ultra-low emission coal-fired power plant, and the mercury emission concentration of wet electrostatic precipitator（WESP） was 0.50～0.58mg/m~3 before activated carbon injection. Activated carbon injection experiments were also carried out at two points. The first location was after selective catalytic reduction device（SCR）and before air preheater（APH）（350℃）. The second location was before the low temperature economizer（LTE）and after the APH（121℃）. The mercury concentration after WESP could reach as low as 0.11mg/m~3, when the activated carbon was injected before the LTE. The results show that the effect of temperature on the adsorption and removal of mercury using activated carbon is more important than that of residence time.Compared with the injection after SCR, the removal efficiency of mercury in the flue gas is higher by the injection of activated carbon in front of the LTE.