To analyze the transient electromagnetic response of shielded cables in time domain when they are subjected to electromagnetic pulse, a frequency domain equivalent method based on minimum phase method is studied in this paper. First, by establishing the circuit model of the transfer impedance testing system, the transfer function of the system in frequency domain is derived, and it is verified as the cascade of a minimum phase system and an all-pass system. Secondly, the minimum phase of the measured amplitude-frequency curve is reconstructed by using the minimum phase method, then the phase of the reconstructed transfer function is compensated according to the distribution of zeros and poles. Finally, the time domain response of the shielded cable is obtained after multiplying the compensated transfer function with the transient interference signal in frequency domain and transforming into time domain. The effectiveness of the proposed method is verified by simulation and experiment.