The dye – sensitized solar cell (DSSC) is an attractive and promising device for solar cell applications that have been intensively investigated worldwide. DSSC consists of a namo TiO2 film of the photo electrode, dye molecules absorbed on the surface of TiO2 film, an electrolyte layer and a Pt counter electrode. Among these, the nanoporous TiO2 film plays an important role because it can adsorb a large amount of dye molecules which provide electrons. Therefore, the TiO2 film affects the cell performance. In this paper, the characteristics of DSSCs with different TiO2 film thicknesses were studied by using electrochemical impedance spectroscopy(EIS). The impedance component attributed to TiO2|electrolyte interface indicated that the small semicircle and low characteristic frequency was essential for high performance DSSC. An optimum overall conversion efficiency( ％) of 5.54% was obtained in the DSSC assembled with the TiO2 film thickness of 8.86μm.