Abstract: This paper proposes a new speckle reduction algorithm for Synthetic Aperture Radar (SAR) images. It is based on the Non Local (NL) means filter and improved by Structural SIMilarity (SSIM). Structure information is introduced into the despeckling method by measuring the similarity between small patches with SSIM. Some experiments on real SAR images, comparing with GammaMAP filter, Contourlet Hidden Markov Tree (CHMT) method, Bayes Least Squares-Gaussian Scale Mixtures (BLS-GSM) method and NL-means filter, demonstrate that the proposed algorithm is able to reduce efficiently speckle while retain edges and structures well.