Abstract: The analysis of electromagnetic disturbance effect for communication systems in the presence of electromagnetic pulse（EMP)was usually complicated in the traditional field circuit method.An equivalent circuit based approach was presented to fast calculate the timedomain response of dipoles in the communication system.The antenna equivalent circuit and the equivalent interference source for EMP were derived respectively，thus time-domain current response in the antenna input port could be efficiently obtained with a simple circuit.Two different dipole structures were taken for validation.By comparing the results of the equivalent circuit with simulated data obtained from a full wave analysis，the equivalent circuit approach was much faster and the circuit parameters could also be easily adjusted.Moreover，the equivalent circuit can be directly connected to the internal circuits of communication system and it could speed up the electromagnetic susceptibility assessment.