Abstract: A Structure Preserving Bilateral Filtering (SPBF) is proposed to address the problem of preserving structural information for reducing speckle in a PolSAR image. The edge structural characteristics and surface scattering features are adopted to measure structural information in PolSAR image, which can reduce loss of structure and improve filtering performance. To begin with, the edge direction is determined by edge templates, and then an adaptive direction window is selected in span image. Furthermore, each scattering mechanism of the pixel is obtained by Freeman-Durden decomposition. And then surface scattering map is obtained by statistical distribution characteristics of polarimetric data. Finally, the filtering mask, which combines the cluster map with adapted direction window, is introduced into an improved bilateral filtering. The experimental results of real SAR images show that the proposed method can efficiently reduce speckle, and further preserve image edge, the strong point target and polarimetric scattering characteristics.