An evaluative method was elaborated for the kinetics description of the selective catalytic reduction (SCR) of nitrogen oxides, being present in the exhaust gases of stationary sources. The volumetric ratio of NO and NO2 was roughly one in the simulated flue gases. Data on the denox reaction of this type of exhaust gases can hardly be found in literature. It was proved that the reduction rate can be fairly well described with the help of a power rate type kinetic equation. The kinetic data of NO-NO2-NH3 reaction on V2O5/TiO2 catalyst show that the reaction rate depends linearly on the NOx concentration (order = 1.07), to a smaller extent on the ammonia concentration (order = 0.73), and it is practically independent of the oxygen concentration. The used catalyst particles of 3 mm characteristic size show a considerable intraparticle diffusion hindrance, it has not an influence on the total reaction order.