In this paper, cobalt oxide was deposited on the surface of Activated Carbon Fiber (ACF) by adsorption and was then sintered. The effects of cobalt oxide on the properties of ACF were studied by XPS, FTIR, and XRD methods. Mercury removal performance was also investigated. 5% cobalt was well dispersed on the surface of ACF, and a variety of oxygen-containing groups had been enhanced. The chemical functional groups on the surface of ACF were changed to strengthen the adsorption and catalytic oxidation of ACF to the element mercury (Hg0). The measurement results showed that ACF coated with cobalt oxide had higher adsorption properties.