The effects of carbon addition on CoMo catalyst performance for sulfidation and hydrodesulfurization (HDS) were investigated. The carbon-containing catalyst was prepared by impregnation of γ-Al2O3 support with NH3 aqueous solution containing Co(NO3)2·6H2O, (NH4)6Mo7O24·4H2O and ethylenediamine. The results indicated that the incorporation of proper carbon on CoMo catalyst can improve its HDS performance. The carbon species on the catalyst were characterized by temperature-programmed oxidation and reduction, temperature-programmed desorption of ammonia and ultraviolet-visible diffuse reflectance spectra. Two forms of carbon species were differentiated: one is spread over the catalyst surface, similar to coke formed from reaction; the other interacts with active phase as an intermediate support. The carbon species acting as intermediate support may decrease the interaction of active metals with support, which enhances the sulfidation and HDS activities of CoMo catalyst.