Abstract: An improved speckle reduction algorithm for polarimetric SAR image based on the local adaptive processing is proposed. This algorithm automatically adjusts the size of the filter window according to distributed characteristic of the pixels in and around the window in the span image. The window size is expanded in the homogeneous area to suppress speckle noises, while the window size is reduced in the area that contains abundant details. This algorithm has the advantages of effectively reducing the speckle noise and keeping the detail. Experiments demonstrate the effectiveness of the proposed method.