The effects of addition of CO on photocatalytic reduction of NO over TiO2/Silica gel photocatalyst have been determined in an annulus fluidized bed photoreactor. The NO reduction efficiency increases with the addition of CO gas in the fluidized bed of TiO2/Silica-gel photocatalyst and the optimum molar ratio of CO/NO for the NO reduction is found to be 1.2. The addition of CO gas is an effective means for N2O degradation and reduces unreacted CO gas slip in the annulus fluidized bed photoreactor.