The invention relates to a particulate oxidation catalyst (POC) postprocessor using metal carriers with one buffer gap and a preparation process thereof, which is characterized in that the carriers are alternately stacked up in a carrier shell by one, two or three kinds of substrates, the buffer gap is arranged in the carrier shell, and the entrances and the exits of the metal carriers as well as the buffer gap are all provided with foam metal cakes-A type carriers; the carriers are coated by oxidation catalyst coatings; the foam metal cakes-A type carriers at the entrances and the exits as well as on both sides of the buffer gap are welded and fixed with the carrier shell by metal retaining rings. The carriers have high mechanical strength and ensure the exhaust smoke of the engines to be reduced by 51-72% when being applied to the vehicle POC postprocessors. The postprocessors are free of backpressure; under the condition of equivalent performance, the price is equivalent to 1/4-1/5 of the price of imported products, thus saving the cost.