Potassium-modified FeCrAl alloy wire mesh was developed as a catalytic diesel particulate filter to suppress the emission of soot from a diesel engine. Potassium species were deposited on wire mesh by a chemical vapor deposition method, in which a model soot was used to convert KOH into metallic K at high temperatures to subsequently activate the wire mesh. Tests showed that metallic K reacted with the enriched Al2O3 component on the surface derived from segregation and successive oxidation during precalcination. The resulting layer of K-O-Al species offers remarkable activity and stability for the catalytic oxidation of diesel soot. The K-activated wire mesh could lower the initial temperature of soot combustion and maintain the activity for several cycles.