To solve the computational demands of spectral clustering approach when applied to SAR image segmentation，a multiscale method is proposed.It consists of three steps，i.e.coarsening，initial segmentation and refining.First，a sequence of smaller graphs，each with fewer vertices，is constructed from the SAR image.Second，spectral clustering is applied on the smallest graph to obtain initial segmentation.Third，the initial segmentation is refined scale by scale to get the final segmentation of the SAR image based on the posterior probability of classification which is estimated by the mixture model.Finally，experimental results demonstrate the effectiveness of the proposed method.