Abstract: The two way parabolic method is the main calculation formulation for radio wave propagation analysis in complex environment. In this paper a new algorithm to solve two way parabolic is proposed for radio wave propagation analysis under irregular terrain. The algorithm recorded the history paths of all wave fronts in the process of the calculation, and according to the each path modified the phases of the two way radio waves respectively. Furthermore the algorithm also reprocesses the boundary condition on the barrier surface in the process of calculation, and improved the staircase model in common use. The results of the method of moments are used to compare with the calculation of the two way parabolic method in different polarization as verification means . The results show the accuracy and advantage of the new algorithm under the irregular terrain.