Abstract: SAR image ortho-rectification in the areas where it is difficult to select points, such as hilly and mountainous terrain, often adopts the method based on the image simulation. The traditional method used the RD model to do the simulation but it needed to establish different modules to do the simulation and ortho-rectification for differents SAR images. This paper proposed the method using the RPC model substituting the RD model to simulate the SAR image in order to address the problem and did the ortho-rectification with the simulated image. Also, this paper improved the method of obtaining gray information from the simulated SAR image. TerraSAR-X images acquired over Sichuan were used as test data. Through the comparision between the actual accuracy and the theoretical accuracy of the ortho-rectification image, the theory and method proposed in this paper were verified.