Abstract: Due to the fact that classical active contour models for SAR image segmentation are highly dependent on statistical distributions,a novel active contour model based on pairwise region similarity is proposed and used for SAR images segmentation.First,the image is over segmented into small homogenous regions.Then,a region similarity measure based on intensity and texture is defined and employed to construct an energy functional.Finally,an efficient regularization and curve evolution method based on over segmentation is enforced to improve the numerical accuracy and evolution efficiency.Experiments on SAR images show that our proposed model can both efficiently and accurately segment SAR images.