The influences of the physical features and chemical properties of activated carbon on Hg-0 adsorption were investigated. The textural characteristics of the samples were studied by Brunauer-Emmett-Teller analysis and scanning electron microscopy. The chemical properties of the samples were characterized by energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results show that the oxygen-containing functional groups on activated carbon have a great influence on Hg-0 adsorption and the functional groups increase the acidity, polarity, and hydrophobicity of the carbon surface and promote the Hg-0 adsorption. The Hg-0 adsorption of activated carbon mainly manifests as chemical adsorption. The desorbed activated carbon almost has no Hg-0 removal ability although it still has a huge surface area and a microspore structure. The oxygen-containing functional groups on the surface play a key role in Hg-0 adsorption. Among them, carbonyl, carboxyl, and ester groups promoted mercury adsorption, while the phenolic hydroxyl group induced inhibition. The process of Hg-0 adsorption on modified activated carbon could be described with the pseudo-second-order model, which indicated that the chemisorption is the dominant step in the Hg-0 removal process by modified activated carbon. Kinetic calculation results also show that under a given gas condition, modified activated carbon possessed a bigger equilibrium adsorption capacity but displayed poor adsorption kinetics.