The parallel FDTD technique based on the graphics processing unit (GPU) is used to predict the low-frequency (LF) ground-wave propagation over irregular terrains in this paper. First of all, through comparing the prediction results of the smooth earth computed by the serial FDTD algorithm, the technique is verified. Then, with the specific examples, the speedup performance of the parallel algorithm is analyzed. The simulation results show that: the technique can improve the calculation speed greatly for long-distance ground-wave propagation problems. It provides an effective solution for the FDTD application in the wave propagation prediction of large-scale.