Abstract: A semi-analytical combined method based on the topology network is presented to solve the problems of terminal responses of the microstrip line. First，electromagnetic topology model of apertures，cavity and microstrip is built. Then，the apertures can be converted to the equivalent magnetic currents，and the coupling electromagnetic field is expressed by using these magnetic currents and the Green’s functions. Finally，the Baum-Liu-Tesche（BLT）equation is used to calculate the voltage and current，that is，the microstrip line coupling terminal response. The validity of the method is proved by comparing with measured results and other methods. Numerical results show that the response of microstrip line reaches its peak value near the slot and cavity resonance. Moreover，the microstrip line is nearer apertures while the pulse width is narrower and the coupling voltage of the microstrip is bigger.