Abstract: In view of the problems for image content authentication and copyright protection，this paper proposes a fragile watermarking algorithm with high security，which can not only detect but also locate changes in images.The algorithm introduces a method which divides the original image into blocks for the location problems of geometric attacks.In view of the detection for original image operation，it proposes a kind of feature space decomposing method.The algorithm is robust to some limited scale and the intensity operation by choosing coefficients and constructing the extracting matrix，and it can implement blind detection too.The security of the algorithm is validated by the computer simulation.