We conducted the experiment to evaluate the conversion performance de-NOx catalyst for lean-bum natural gas engine. The NOx adsorption catalyst was based on Pt, Pd, Rh with Ba included washcoat. Effective parameter were space velocity, spike period of rich condition, temperature of fluid gas. It was known that there are windows of the gas temperature and
space velocity for the catalyst for the optimum NOx reduction ratio. A evaluation model of de-NOx adsorption catalyst developed to comparing with the conversion performances of the catalysts.