Abstract: To investigate the coupling mechanism between an electromagnetic pulse and a transmission line above the lossy ground, we built an equivalent circuit for the transmission lines above the lossy ground based on the delay extraction-based passive compact transmission-line (DEPACT) macromodeling algorithm. The transmission line above the lossy ground was viewed as a cascade of some transmission line subnetworks. Each transmission line subnetwork was represented by a cascade of lossy and lossless transmission lines. The equivalent circuit for the lossless section existed. The ground impedance was approximated as a rational function by the vector fitting (VF) method, and the equivalent circuit for the lossy section was built by the Laplace Element in HSPICE. The simulation results were compared with the results with the finite difference time domain (FDTD) method and good agreement was obtained. Using this approach, the transient response for the transmission lines above the lossy ground with nonlinear terminations could be obtained easily and accurately.