In this paper, a new watermarking scheme based on Chaos for image authentication and tamper detection is proposed. This scheme can detect any modification to the image and determine the specific location of the modification. In order to improve the security of the proposed scheme, two chaotic maps are used. Because the chaotic map is sensitive to the initial value, the corresponding position relationship between the pixels in the watermarking image and the watermarking is disturbed, which makes the watermarking scheme resist forgery attack. In this scheme, the initial value of the chaotic map is used as the secret key, and the effectiveness of the proposed scheme is checked through a series of attacks. The experimental results show that the scheme is not only safe and reliable, but also can achieve high tamper detection and location accuracy under different attacks.