In this report, an improved method to estimate the equivalent circuit parameters in the dye-sensitized solar cells (DSSCs) is introduced. It is founded that, several different groups of values of equivalent circuit parameters can fit well to the same experiment-measured I-V curve. Furthermore, the gap between some parameter values in those different groups is so large that it reaches up to several orders of magnitude. To eliminate this uncertainty of parameter estimation, an improved method, which based on both the extention of measured range and the computer simulation of current-voltage (I-V) characteristic curves, is proposed to ensure uniquely the values of DSSCs equivalent circuit parameters. A series of I-V curves which derived from the estimated parameters by this improved method fit well to the corresponding experiment-measured I-V curves. The results indicate that, there exclusively exists one group of parameter values for a special DSSCs equivalent circuit, thus demonstrating the validity of the improved method proposed in this work. (C) 2008 Elsevier Ltd. All rights reserved.