Abstract: This paper analyzes the reflection coefficient of the ground surface and dielectric properties of the soil, studies the vehicle structure affects the antenna radiation and gets the impacts of the vehicle model, ground dielectric, distance on the antenna coupling factor, finally establishes a precise communication vehicle model and simulates electromagnetic coupling factor between the sending and the receiving antennas in flat ground situation. Compared with the data from the actual test, it shows that the simulation results can approximately describe the coupling factor of the actual test. The maximal error is 16.54 dB and the mean square error (MSE) is 4.21 dB.