Abstract: Ground penetrating radar(GPR) forward modeling is the basis of inverse modeling and the identification technology of profile. GPR is also the basis for artificial reading engineering drawings. By using it the precision and accuracy in explaining images can be improved. From Maxwell's Equations of rotation which summarizes macroscopic electromagnetic theory, using Yee Network Model and central difference formula, by introducing complex permittivity, the authors deduce two-dimensional UPML absorbing boundary of electromagnetic field discrete difference formula. The forward modeling program based on UPML absorbing boundary twodimensional TM wave is realized by programming language MATLAB. The forward simulation of crushing zone in front of the tunnel and square, round cave is conducted by using the program. Profile features of different geological bodies, rule of reflection, rule of diffraction and propagation characteristics are revealed. The simulation results show that UPML absorbing boundary could effectively inhibit the non-physical reflection of truncating boundary to outstand the effective wave, which is beneficial for engineers to accurately make geological interpretation with the map.