Catalytic filters (CFs) were fabricated by coating manganese and ceria oxides on mullite filters with a high porosity and a relatively low pressure drop and were used in the selective catalytic reduction of NOx by NH3 (NH3-SCR). The influences of Mn/Ce ratios and loading weights were investigated. The CF with a Mn/Ce molar ratio of 6/4 can achieve >90% NO conversion in the temperature range of 120-250 degrees C, owing to abundant surface oxygen species, Ce3+, and Mn4+ on it. NO conversion in the temperature range of 120-250 degrees C increased when the loading weight increased from 1.05 to 4.18%; however, when the loading weight was further increased, the catalytic activity remained unchanged. A possible growth mechanism of catalyst particles on mullite filters was proposed: the active species tended to disperse finely when the loading weight was lower than similar to 4.00%; however, when the loading weight was more than 4.00%, the particles tended to grow at the conjunction of fibers, leading to a considerable pressure drop increase. The CFs showed a dust removal ability of more than 99% in a pilot experiment, which may provide a chance for the coprocessing of dust and NOx in practical use.