The invention discloses an SAR (synthetic aperture radar) image change detection method based on low-rank matrix factorization, and mainly solves the problem that the existing method cannot detect an SAR image change region accurately. The implementation steps of the method include: firstly, performing speckle reduction pretreatment to two SAR images to be detected to obtain smooth SAR images; secondly, constructing logarithm ratio of the two images after speckle reduction; thirdly, performing low-rank sparse factorization of the logarithm ration to obtain a low-rank part and a sparse part of the logarithm ratio; fourthly, transforming the sparse part into a sparse matrix by column; and fifthly, performing clustering to the obtained sparse matrix by the K-means algorithm to obtain the final change detection results. The method has the advantage of accurate change detection region, and can be used in the fields of public security and video monitoring.