A method for in-situ generation of nanoflower-like manganese dioxide catalyst on filter material is provided. The method comprises: immersing a filter material in a solution containing sodium lauryl sulfate and nitric acid; first modifying the surface of the filter material by using the sodium lauryl sulfate so that a charge layer is wound around the surface of the filter material and tightly absorbs H+ in an acid solution; and then adding potassium permanganate as an oxidant to react with H30 on the surface of the filter material to generate nano flower-like manganese dioxide in situ on the surface of the filter material, so as to obtain a composite filter material having a denitration function.