In recent years, many factors lead to the frequency fluctuation accident of power system occurring often. The simulation results of multiple faults show that the estimation error of frequency modulation capability of power system is large at present, so it is necessary to use the power system frequency response (SFR) model to calculate dynamic frequency response. The shortcomings of the classical SFR model are analyzed, and the structure of the SFR model is improved accordingly, in which the dynamic characteristics of the polymer governor are taken into account. Then a parameter tuning method for the improved SFR model is proposed. In this method some parameters are obtained by direct calculation, the parameter equation for keeping steady-state compliance is added, and the other parameters are identified. The structure and parameters of the model are calculated in the simulation example, which verifies the validity of the improved SFR model and parameter tuning. The results indicate that the improved SFR model represent the major characteristics of SFR very well, and its accuracy is much higher than the classical SFR model.