We propose a novel watermarking algorithm based on discrete fractional random transform. Random block selection and high amplitude selection techniques have been employed to improve the robustness of the watermarking algorithm. The imperceptibility of the watermarking is improved by adjusting the intensity of phase shift keying. Simulations under several conditions are given to verify the effectiveness of the proposed scheme. The results have shown the proposed algorithm is robust against the attacks of cropping, noising and low-pass filtering.