Activated semi-coke was developed and loaded by iron species and other assistant metals (Co, La, and Ce) using a hydrothermal method to obtain the abatement of NOx emissions from power plants and then used for NO removal by CO. These catalysts were systematically characterized by N-2 physisorption, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and the activity of NOx reduction. The results showed that the activated semi-coke that was loaded by Fe species could achieve an excellent NOx conversion of 96.5% at 350 degrees C with 0.2g/g (20wt%) of the precursor content (catalyst denoted as Fe20/ASC). This was ascribed to higher amounts of surface Fe3+ and chemisorbed oxygen. Furthermore, Co was the best promoter among Co, La, and Ce. This enhancement was attributed to the increase of the specific surface area and chemisorbed oxygen, as well as the formation of CoFe2O4. The synergistic effect between Fe and Co species was beneficial for the formation of oxygen vacancies, which could promote the adsorption and dissociation of NO. The in situ DRIFTS results indicated that the reaction for NOx removal by CO over activated semi-coke supported catalysts mainly occurred between coordinated nitrates/nitryls and the adsorbed COx species.