This paper proposes a new analytical method to determine the series resistance Rs of solar cells. This method is based on the exponential function of characteristic equation and results are evaluated from the experimental data. The parameter model of series resistance Rs proposed in this paper and other four parameter models (the shunt resistance Rsh, the saturation current Is, the photo current density IL, the ideality factor n) proposed by other authors are more accurate models than the five parameter models all proposed by other authors for solar cells. In order to verify the accuracy of the recombined models presented in this paper, the presented recombined models and other authors' models will be compared. Experiment results show the proposed recombined models are simple, effective and feasible models for solar cells.