The invention provides a preparation method for preparing an aniline conductive polymer in-situ coating denitration filter material PANI (polyaniline) @MnO2/PPS (polyphenylene sulfite) in one step and belongs to the technical field of functional modification of PPS filter materials. Aniline conductive polymer in-situ coating of the PPS filter material is performed while an MnO2 low-temperature denitration catalyst is generated, bonding strength of the MnO2 catalyst and the PPS filter material is increased, and better mechanical performance is attached to the PPS filter material. The surface of the filter material is coated with a layer of a polyaniline film while the MnO2 is formed, and a catalyst layer good in dispersibility and tightly combined with the filter material is obtained; the strength of the filter material is enhanced through the polyaniline film, and the obtained filter material is antistatic in property due to electrical conductivity of polyaniline; when soot is filtered, particle matter is less prone to being adsorbed on the surface of the filter material, and the frequency of regular cleaning of the filter material is reduced.