Kinetic parameters of ammonia adsorption/desorption, NO reduction, and ammonia oxidation are measured, and applied for the steady-state ammonia-SCR Cu-zeolite catalytic models in the simulations. As the oxygen concentration changes due to the EGR and engine load in the real drive operation, the effects of oxygen concentration on the reactions are considered in the model. The calculated results in steady-state conditions are compared with the surrogate gas experiments and the accuracy of the model is verified.