The dynamic characteristics of the gap sensor necessary for suspensive control system in maglev vehicle, are difficult to measure at high frequency by mechanical methods. The eddy current effect of the measured conductor is replaced by the simulative eddy current field. The measurement method of dynamic response based on modem is presented and discussed with sinusoidal signal and impulse adopted. The result of relevant experiments is given. Compared with the mechanical methods, the proposed method is proved to be more effective.