The invention provides a poly (3,4-ethylenedioxythiophene) nanowire thin film. The poly (3,4-ethylenedioxythiophene) nanowire thin film is prepared according to the following synthetic method that in a three-electrode electrolytic cell, a mixed solution of 3,4-ethylenedioxythiophene monomer, a supporting electrolyte and an electrolytic solvent serves as an electrolyte solution, a gold electrode, a platinum electrode and an indium tin oxide conductive glass electrode or a fluorine-doping tin oxide conductive glass electrode serves as a working electrode, the gold electrode or the platinum electrode serves as an auxiliary electrode, a silver/silver chloride electrode serves as a reference electrode, polymerization reaction is conducted through a cyclic voltammetry or a potentiostatic method at the room temperature, and thus the poly (3,4-ethylenedioxythiophene) nanowire thin film deposited on the working electrode is obtained, so that a finished product is obtained after post-processing leaching and drying are conducted. According to the poly (3,4-ethylenedioxythiophene) nanowire thin film, the preparation method is simple and convenient, the reaction condition is mild, the product purity is high, and the prepared polymer thin film has an electrochromic performance and can be used as an electrochromic material to be applied to an electrochromic device.