The role and effect of simulated flue gas on adsorption of elemental mercury (Hg0)on coconut shell activated carbon (CS-AC)were studied by adsorption experiment carried out at 130℃ in a bench-scale fixed bed to reveal the characteristics of homogeneous/heterogeneous oxidation reaction between components of simulated flue gas，Hg0 and CS-AS surface.The experiments were divided into three parts：first，adsorption of Hg0 on surface of CS-AC in nitrogen (N2)gas and simulated flue gas; second，homogeneous oxidation reaction between the components of simulated flue gas and Hg0; and third，adsorption of Hg0 in N2 gas on surface of CS-AC pre-adsorbed by simulated flue gas.The results showed that CS-AC can not adsorb Hg0 in N2 gas，however，it became easy in simulated flue gas and the initial adsorption efficiency was up to 80%.According to the result of homogeneous reaction between the simulated flue gas and Hg0 at the temperature of 130℃，only about 14% of Hg0 can be oxidized to divalent mercury (Hg2+)which is easily adsorbed by CS-AC，which was much lower than 80% of initial Hg0 adsorption efficiency in the simulated flue gas.This result could indicate that homogeneous reaction between simulated flue gas and Hg0 was not the main reason of high Hg0 adsorption efficiency.It was very interesting that in N2 gas Hg0 could be adsorbed by CS-AC if it was pre-treated with simulated flue gas without Hg0.The pre-adsorption process of simulated flue gas could fix some components in flue gas，such as NOx，etc.，on surface of CS-AC，and these components would help adsorption of Hg0 in N2 gas，and the initial adsorption efficiency was about 67%.During the oxidation adsorption process，surface of CS-AC played important role.Therefore，it could be thought that the adsorption process of Hg0 by CS-AC is a heterogeneous chemical oxidation reaction and adsorption process between oxidizing components in flue gas，element mercury Hg0 and the CS-AC’s surface，whatever in N2 gas or in simulated flue gas.