Metallic substrate is with the advantages of fast burning, small volume, high mechanical strength, prominent heat-resistance, etc. It is widely used in exhaust gas purification, especially for motorbike. Firstly metallic substrate should be pretreated in order to generate a transition layer which is required to solve the mismatched heat expansion between metallic substrate itself and the active layer. On the transition layer, it is coated with rare earth catalyst, while in active layer is coated with noble metal like Pt,Pd,Rh. It can meet Euro 2, 3, 4, 5 emission standard, and OBD-2 system for EPA, CARB emission standard.