The invention discloses a preparation method of a zinc-modified tungsten trioxide thin film photoelectrode, belonging to the field of preparation of inorganic photoelectrode materials. The preparation method disclosed by the invention is characterized by taking ITO (indium tin oxide) conductive glass as a substrate, taking an amorphous tungsten oxide thin film prepared by adopting an electrodeposition method as a basal body, uniformly modifying zinc on the amorphous tungsten oxide thin film through an impregnation method, and then performing heat treatment at a certain temperature in the air to obtain a novel zinc-modified tungsten trioxide thin film photoelectrode material. After the WO3 is modified by the Zn, a layer of ZnO thin film is formed on the surface of the WO3; and as the position of a valence band of the ZnO is more negative in comparison with the WO3, when light irradiates the thin film electrode, a photohole in the valence band of the WO3 can flow into the valance band of the ZnO under the action of electric field force, thus the compounding of photo-induced electrons of the WO3 and the hole is inhibited, and the purpose of improving photoelectric conversion efficiency and photoelectric catalysis capability is achieved. The preparation method disclosed by the invention has the advantages that the prepared thin film is uniform and good in adhesion with the substrate; and equipment adopted by the preparation method is simple, easy to operate, low in cost, environment-friendly and the like.