In this paper,we proposed a novel image hash algorithm based on Zernike moments.We employ Zernike moments to represent the image content for the reason that it is the projection of the image under a group of orthogonal basis.Thus,the discrimination of proposed algorithm is improved.Meanwhile,benefited from the invariance property of Zernike moment under affine transform,our algorithm is robust to rotation attack.In the proposed method,the hash string is generated from the Zernike moments of the normalized input image.Secret key is also introduced to ensure the security of the hash method.In the experiments,the method is tested by 100 sample images.The false accept rate under rotation attack is less than 4%.The error recognizing rate between different images is about 10-9.Experimental results prove that our algorithm has great robustness and discrimination.