NOVELTY - A composite film counter electrode comprises a conductive base (1), a manganese dioxide thin film (2) and a conductive polymer thin film (3) connected from bottom to top through the inter-molecular force and the inter-atomic force in sequence.    USE - A composite film counter electrode for dye-sensitized solar cell.    ADVANTAGE - The electrode has excellent catalysis effect, is low cost, and has a photoelectric conversion efficiency of 3.85%.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method of preparing a composite film counter electrode comprising:    (A) dispersing manganese dioxide powder (6-7 g) in an aprotic organic solvent (350 ml), adding tetrabutyl ammonium hydroxide, stirring for 24 hours, aging for 1 hour, subjecting to centrifuge, drying, dispersing dried manganese dioxide powder (6-7 g) in aprotic organic solvent (150 ml), performing an ultrasonic oscillation for 20-40 minutes, aging for 20-40 minutes to obtain suspension manganese dioxide electrophoresis solution;    (B) subjecting manganese dioxide electrophoresis solution with a conducive base as the anode, platinum electrode as the cathode maintained at a distance of 0.5-1.0 cm to electrophoresis for 3-5 (preferably 4) seconds at a direct current voltage of 40-60 V to deposit the manganese dioxide thin film on the conductive base, drying the conductive base at 70-90 degrees C for 20-24 hours to obtain manganese dioxide thin film;    (C) dissolving conductive polymer monomer (15-20 mmol/l) in boron trifluoride ether to obtain the conductive polymer monomer electro-deposition solution, performing cyclic voltammetry the conductive polymer monomer electro-deposition solution for 10-20 cycles, speed of 0.05 rpm, at - 0.8 to 1.6 V using electrochemical workstation as a tri-electrode system, conductive substrate deposited with manganese dioxide thin film as working electrode, platinum electrode as counter electrode, saturated electrode of silver/silver chloride electrode as reference electrode; and    (D) taking out the working electrode, cleaning with deionized water, drying at 70-90 degrees C for 10-15 hours.