Abstract: A registration method for SAR image based on cascade filter and relaxation optimization algorithm is proposed in this paper.Firstly,the cascade filter method combining partial differential equation(PDE) and enhanced Lee filter is introduced for SAR image speckle reduction.Then edge extraction is done in the filter result of object image.Every feature point of the edges is matched by the relaxation optimization algorithm,a pyramid matching strategy is employed for the accuracy simultaneously.The experiments show that the method can reach a good registration result.