Gaseous mercury removal from simulated flue gas by sorbent injection was estimated and the effect of an electric field applied to a particulate collector on mercury removal was analyzed. For this, a bench scale system which included a sorbent injection reactor and a hybrid particulate collector was made up. The hybrid particulate collector consisted of an electrostatic precipitator and a fabric filter. Activated carbon was injected into the reactor as a sorbent. According to the result of experiment using simulated gas prepared by injecting gaseous mercury into air, the mercury removal by activated carbon injection at 130 ℃ varied from around 3.9% at C/Hg ratio of 1,000 up to around 24.4% at C/Hg ratio of 50,000 including reaction in the hybrid particulate collector. When C/Hg ratio was fixed at 10,000 and temperature was changed from 50 ℃ to 150 ℃, the mercury removal decreased from 43.2% to 1.9%. In addition, when high voltage was applied to the hybrid particulate collector, the mercury removal increased up to 63.1% at a C/Hg ratio of 5,000 and at a temperature of 130 ℃. Considering baseline mercury removal efficiency of up to 50% in the utility boilers due to the acid gases containing in the flue gas, above results indicate that 90% or more of gaseous mercury could be removed.