Abstract: In view of the question of images' authenticity, an effective and robust image identification algorithm is presented based on digital signature. Firstly, image is preprocessed to enhance the capability of images' anti-JPEG compression. Then the image is divided into two regions equally, and the top five of image's block average value are extracted and mapped to the element of GF(25) to construct the RS code. The generated check code is scrambled by Arnold transform as digital signature to authenticate the original image. Experimental results show that the algorithm not only can detect whether the content of the image is tampered or not but also can accurately locate the tampered position, which improves the image on the robustness of JPEG compression. Thus this algorithm can effectively distinguish JPEG compression operation from the deliberate tampering.