Pt counter electrodes (CEs) with different platinum loading have been prepared using chemical reduced method on flexible indium-doped tin oxide coated polyethylene naphthalate (ITO-PEN) for dye-sensitized solar cells (DSSCs). H2PtCl6 center dot 6H(2)O terpineol solutions were screen printed on the transparent ITO-PEN substrates. After drying, H2PtCl6 was reduced by treating it in NaBH4 solution followed by the hydrothermal treatment at 100 degrees C. The obtained Pt CEs with different Pt-loading (2.4-7.7 mu g/cm(2)) were characterized by SEM, XPS, electrochemical impedance and transmission spectrum measurement. The Pt CEs show high catalytic activity, low charge transfer resistance (0.26-1.38 Omega cm(2)) and good light transmittance (about 70% at 400-800 nm). The light-to-electricity conversion efficiency of the flexible DSSC fabricated with the prepared Pt CE and the TiO2 photoanode prepared on Ti substrate by screen printing technique attains 5.41% under the simulated AM 1.5 sunlight, which is almost same as that based on the thermal decomposited Pt CE on FTO-glass. Compared with other methods to prepare Pt CEs, chemical reduced method is simple and suitable for flexible polymer substrates and the large scale preparation of DSSCs. (C) 2010 Elsevier Ltd. All rights reserved.