Abstract: The present invention relates to a novel catalyst composition for use in a nitrogen oxide removal unit (DeNOx), a diesel particulate filter (DPF) and a diesel oxidation catalyst (DOC) unit, as well as a diesel exhaust after-treatment system comprising the same. In the diesel exhaust after-treatment system, the catalyzed ceramic filter ha s a low balance point temperature, and thus it can be operated even at low temperatures without an increase in back pressure. At a lower temperature, it can be continuously regenerated by the injection of heated light oil without applying excessive load to engines. Also, it can efficiently remove carbon monoxide and hydrocarbon with a high efficiency at low temperatures.