A digital watermarking algorithm based on depth perceptual region of interest (DP-ROI) for copyright protection of three dimension (3D) images is proposed. First, DP-ROI is defined according to the three-dimensional depth sensation of human visual system and extracted through depth image and gray image. Then, gray image is transformed with discrete cosine transformation (DCT). Several middle frequency DCT coefficients in DP-ROI are adjusted with smaller strength to embed watermark. Finally, by computing the correlation of DCT middle frequency coefficients, and blind watermark is extracted. The experimental results show that the proposed watermarking algorithm has good robustness against image processing attacks, such as JPEG compression, Gaussian noise addition through selection of watermark embedding strength.