Abstract: Aiming at the bug of current block based fragile watermarking scheme，a novel fragile watermarking scheme based on chaotic hash function is proposed in this paper.Firstly chaotic hash function is implemented on each image block to generate binary image，then XOR the binary image with the chaotic binary image generated by chaotic system to attain binary fragile watermark，after being scrambled，the binary fragile watermark is embedded into LSB plane of original image；difference image is used to realize authentication.Theoretical analysis and experimental results show the proposed scheme has good invisibility，and ability of resisting VQ attack，differentiating the tamper type，even the super security.