Being aimed at the tamper location accuracy and the security problem of existing fragile watermarking authentication algorithms, an image authentication scheme is presented which can separate tamper detection and tamper location. Let the grayscale value of the host image as the initial value of the chaotic mapping to generate detection watermarking image and location watermarking image, then embedded them into the Hypo-LSB and LSB of each pixel. The proposed scheme can locate the tampers on the watermarked image accurately by using the high sensitivity on initial value of chaotic mapping. Moreover, no host image is needed in watermark extraction. The experiment results demonstrate that the fragile watermarking arithmetic can detect any change to image pixel value and any destroy to image completeness, and also can locate tampered area in pixel-level accurately.