Using the DFT calculations, we explore the possibility of using a porous Si-decorated carbon nitride fullerene (Si@C24N24) as a potential catalyst for reduction of N2O. Our results indicate that Si atom is stably anchored in the N-4 cavity of C24N24 with a large adsorption energy of - 6.85 eV. A N2O molecule can be easily dissociated into N-2 and O-ads species over the Si atom of Si@C24N24. The activation energy for the removing of O-ads by CO molecule is only 0.37 eV. Moreover, the reduction of N2O by CO can be selectively performed in the presence of H2O and O-2 molecules.