In order to construct a high-efficiency paper catalysts for soot removal, it is very important to design different active elements and realize the synergistic effects with the matrix fibers. A series of La1-xKxMnO3 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) nanofiber catalysts were prepared via electrospinning. The oxidation performance of the catalyst for soot particles was examined by temperature programmed oxidation reaction. The defect effects induced by doping K+ ions in the LaMnO3 lattice on their catalytic performance evaluated by soot temperature-programmed oxidation were investigated by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and temperature programmed reduction analysis. The results show that all the nanofiber catalysts have a perovskite structure, while K2Mn4O8 as a new phase appears in the samples as x ≥ 0.3. The amount of active oxygen in the sample is affected by K+ ions replacing La3+ ions and Mn3+ ions transferring into Mn4+ ions. The replacement of A-site ions increases the degree of oxygen defects in the system, while the transformation of Mn3+ ions into Mn4+ ions determining the number of oxygen vacancies as a new phase can occur at a great content of K+ ions doped in the system. The sample La0.6K0.4MnO3 has an optimum catalytic activity at T50 of 347 ℃. The paper-structured catalyst prepared with a nanofiber to matrix fiber ratio of 1:1 has a good catalytic activity at T50 of 478 ℃.