The invention discloses a method for preparing polyaniline and modifying a lead storage battery positive pole plate. The polyaniline is prepared by aniline oxidization of lead dioxide in a sulfuric acid solution, the generated polyaniline is dispersed and mixed in a lead powder material to obtain a polyaniline-dispersed lead paste material, the polyaniline-dispersed lead paste material is directlyused as a raw material of a storage battery positive active substance and is coated on a positive grid, the polyaniline-modified positive green plate is obtained by coating, filling, curing and drying, the positive green plate is used for performing electrochemical formation of an electrochemical formation liquid in a rare-earth ion-containing sulfuric acid aqueous solution, during the battery formation process, a lead compound on the positive green plate is converted to the lead dioxide, meanwhile, a variable-valence rare-earth ion RE<3+> is subjected to oxidization reaction at a positive electrode to generate RE<4+>, the positive grid and the positive active substance of the positive pole plate are further modified by the generated rare-earth high-valance substance, the positive electrode material is synergically modified by the polyaniline and a rare-earth element, and the performance of the lead storage battery is improved. The method is simple, the polyaniline is easily and uniformly mixed and added into the electrode active substance, a small amount of rare earth is uniformly and quantitatively doped to a surface of an electrode, the surface performance control of the electrode is achieved, the equipment investment is low, and the process is greatly improved.