The Kirchhoff migration plays an important role in converting seismic data into images of geological layers according to viewpoint in the applied geophysics. In this paper, the application of the Kirchhoff migration was used in the case of the high frequency electromagnetic method for specifying GPR velocity model. The measurements of raw GPR data collected by Ramac X3M with 500 MHz frequency in HoChiMinh city were processed on the basis of the Kirchhoff migration to velocity model by establishing a set of different velocities. The migrated results of a diffraction case were analyzed to choose the optimal velocity. The optimal velocities of being chosen from Kirchhoff migration in two cases were considered medium environment velocities.