The effects of the zeolite-supported precious metal catalysts on NOx reduction in oxygen-rich exhaust have been investigated. It became clear that NOx conversion related the number of NO adsorption sites of precious metal and the number of HC (C3H6) adsorption of support (zeolite). Pt-Ir-Rh/MFI zeolite catalyst showed higher performance and durability than the current Pt-Rh supported on alumina and ceria catalyst.