The carbon-nitric oxide (NO) reaction plays an important role in many processes where the reduction of NO is attempted. In all cases, there is a certain amount of oxygen that significantly increases the rate of C-NO reaction. The objects of this study are to clarify the role of oxygen gas and to elucidate the reaction mechanism by analyzing the surface species. It was found that the formation of surface oxygen complexes by the C-O2 reaction is essential for the C-NO reaction. In addition to oxygen complexes, a considerable amount of nitrogen was also trapped in the carbon matrix during reaction. In the initial stage of the reaction, the concentration of nitrogen-containing product gas was much lower than expected from the NO consumption. The surface nitrogen species were identified by X-ray photoelectron spectroscopy as pyridinic, pyrrolic or others. These are rather stable in an inert atmosphere even at 950-degrees-C, but they can easily be removed at 600-degrees-C in the NO- or O2-containing reaction atmosphere.