The principle of the ground wave propagation for Electromagnetic Pulse(EMP) is presented. The propagation function of ground wave varying with the distance and frequency is developed as the ground conductivity above 0.005 S/m, and the EMP ground wave of nuclear explosion at different distances are computed. The results show that the amplitude of the propagation function is reduced with the increasing of frequency and distance, and the EMP ground wave is attenuated by ten times at a distance of 500 km from nuclear explosion location.