NOVELTY - 3,4-Ethylenedioxythiophene monomer and mixture of boron tetrafluoride and tert-butylamine are dissolved in acetonitrile solvent and blended uniformly, to obtain electrochemical solution. The electrochemical solution is poured into an electrochemical reactor which uses silver/silver chloride as reference electrode and stainless steel or platinum as counter electrode, and electrodeposition is carried out. Poly(3,4-ethylenedioxythiophene) is deposited on the surface of indium-tin metal oxide conductive glass to form poly(3,4-ethylenedioxythiophene) thin film.    USE - Preparation of poly(3,4-ethylenedioxythiophene) thin film used for photoelectric device.    ADVANTAGE - The poly(3,4-ethylenedioxythiophene) thin film is easily formed on surface of conductive glass, in short time.    DETAILED DESCRIPTION - 3,4-Ethylenedioxythiophene monomer and mixture of boron tetrafluoride and tert-butyl amine are dissolved in acetonitrile solvent and blended uniformly, to obtain electrochemical solution containing (in weight%) 3,4-ethylenedioxythiophene (0.001-0.1), mixture (0.25-2.5) of boron tetrafluoride and tert-butylamine and remainder of acetonitrile. Alternately, 3,4-ethylenedioxythiophene, boron trifluoride and polystyrene sulfonate are dissolved in ether solvent and blended uniformly, to obtain electrochemical solution containing 3,4-ethylenedioxythiophene (0.001-0.1), boron trifluoride (45-50), polystyrene sulfonate (0.001-1) and remainder of ether. Alternately, the acid supporting electrolyte and polystyrene sulfonate are added to deionized water, blended uniformly, 3,4-ethylenedioxythiophene is added and blended uniformly, to obtain electrochemical solution containing 3,4-ethylenedioxythiophene (0.001-0.1), acid supporting electrolyte (1-25), polystyrene sulfonate (0.001-1) and deionized water. The acid supporting electrolyte is sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid or acetic acid. The electrochemical solution is poured into an electrochemical reactor which uses silver/silver chloride as reference electrode, stainless steel or platinum as counter electrode and indium-tin metal oxide as work electrode of conductive glass, and electrodeposition is carried out at voltage of 0.7-1.2 V and current density of 0.05-0.5 nA/cm2 for 10-600 seconds. Poly(3,4-ethylenedioxythiophene) is deposited on the surface of indium-tin metal oxide conductive glass to form poly(3,4-ethylenedioxythiophene) thin film.