Abstract: JPEG image is one of the commonly used image format. Because of the less redundant data, the length of authentication watermark for JPEG images authentication should be as short as possible. In this paper, combined with matrix encoding and multiple watermarking, a block-level authentication algorithm for JPEG images is proposed. Matrix encoding can shorten the length of the watermark magnitude and accurately locate one information change. And then multi-watermarks are generated for the tampering of the image block authentication. The detailed analysis is given about the missing rate and the false detection rate in this paper. Theoretical analysis and experimental results show that the JPEG images block-level tamper localization can be done under the lower tamper rate. The missing rate and the false detection rate are at the 10-2 level, even if 2 bits watermark are embedded in the rate of tampering is less than 5%.