In order to accurately analyze the high frequency modulation response of laser diode (LD) in high speed communication, it is necessary to take the effect of the parasitic network into account. In this paper, the relation between the scattering parameters of laser measurement system and the transfer function of intrinsic response is deduced. By combining the rate equation with its equivalent circuit model, a new method for extracting the intrinsic response of laser and simulating the modulation response of the overall laser diode is proposed. The advantage of this method lies in that there is no need to measure the parasitic network separately and estimate the circuit parameters of active region. The results of measuring Fabry-Perot (F-P) laser sample are in good agreement with the simulation, which indicates that the method is simple and accurate.