The invention provides a tungsten trioxide/polyaniline core-shell nanowire array radiochromic film and a preparation method thereof. The preparation method comprises the following steps: dissolving white tungstic acid in aqueous hydrogen peroxide liquor to prepare peroxide tungstate liquor; coating the peroxide tungstate liquor on an electric conductive face of a clean electric conductive substrate; dissolving tungstate in alcohol to form precursor liquor, fixing the electric conductive substrate in a reaction kettle, adding the precursor liquor into the reaction kettle, carrying out a reaction at 150-250 DEG C for 8-16 hours, and taking out and carrying out thermal treatment at 300-450 DEG C for 1-3 hours to obtain a tungsten trioxide nanowire array; and mixing aniline and dilute sulphuric acid to form electrolyte for preparing polyaniline and carrying out electro-polymerization on polyaniline to obtain the tungsten trioxide/polyaniline core-shell nanowire array radiochromic film. The preparation process is convenient to control, lower in preparation cost and easy to realize industrialization. The film has the advantages of large spectrum adjustment range, abundant radiochromic types, high coloring efficiency, fast response speed, long cycle life and the like.