The invention discloses a preparation method of a sepiolite/polyaniline nanocomposite material. The preparation method is characterized by comprising the following steps: mixing sepiolite with water, standing, filtering an upper-layer sepiolite suspension liquid, washing with water, and drying to obtain washed sepiolite; mixing the washed sepiolite with hydrochloric acid, stirring in a water bath, filtering, washing solids with water, and drying to obtain acid activated sepiolite; mixing the acid activated sepiolite with an organic solvent, adding amino-carrying silane coupling agent, mixing, stirring in the water bath, filtering, washing, and drying to obtain organized modified sepiolite; mixing the organized modified sepiolite with water into a dispersion liquid; adding a dopant and phenylamine while stirring, cooling, adding an oxidant for stirring, reacting and then washing and drying materials, to obtain a product sepiolite/polyaniline nanocomposite material. The prepared composite material has high electric conductivity and high specific capacitance, and is applicable to the fields of a supercapacitor electrode material, a secondary material, an electromagnetic shielding material and the like.