The simulation of electromagnetic wave propagation is an interesting field, particularly for the study of various propagation problems, including application in Ground Penetrating Radar GPR, which represents our general focus of study. The calculation techniques used to propagate the wave are numerical methods applied to Maxwell’s equations, we can adopt the finite difference method (FDTD) to solve differential equations and to solve integral equations, the finite element method can be used. The wave phenomenon is characterized by optical phenomena, we specify the phenomenon of the reflection which will take place each time the wave meets a new medium of propagation, this phenomenon appears essential for the radar measurements. However, for a limited calculation space, reflection at the boundaries becomes a parasitic phenomenon that must be suppressed. During this work we will implement CPML absorbing boundary condition with the FDTD method to study the propagation of an electromagnetic wave in the ground.