Abstract: Based on the hypercomplex Fourier transform(HFT),a novel frequency domain watermarking algorithm for color host images is proposed.The watermark data are embedded into some proper hypercomplex frequency components and their corresponding HFT coefficients are modified to fulfill the symmetry constraint.The prerequisite,the watermarked host image in spatial domain should also be transferred in red,green,and blue channels,of embedding watermark data into the hypercomplex frequency domain is obtained.The analytical results show that the image distortions from the watermark are spread throughout the whole image and are spread into the three channels of a color host image by a hypercomplex inverse Fourier transform.So the proposed watermarking algorithm can realize a good combination for the imperceptibility and security of the watermark.Moreover a cross redundancy embedding rule is also proposed to improve watermarking robustness further.Experimental results verify the effectiveness and superiority of the proposed algorithm.