Abstract: By combining quaternion Fourier transformation with quaternion singular value decomposition and introducing them into the color image watermarking processing,a blind color image watermarking algorithm is proposed based on the quaternion singular value decomposition in frequency domain.The color host image is divided into blocks and the relative matrix in the frequency domain is obtained by the quaternion Fourier transformation firstly.Then the unit blocks of the matrix in the frequency domain are decomposed by quaternion singular value decomposition(QSVD) to get singular values with real coefficients.The method of odd and even quantization index modulation is applied to embedding the watermark signals into the maximal singular value of each unit block.Experimental results demonstrate that the watermarks are spread into all color components in the spatial domain and the proposed watermarking scheme is better than traditional luminance watermarking algorithms and separate channel watermarking algorithms in robustness and imperceptibility.