Digital watermarking plays an important role in image verification and copyright protection. A watermarking scheme for authenticating ROI (region of interest) of image has been proposed in the paper. To embed the watermark in the interior of ROI, Poisson matting technique is introduced to extract the region of interest of image. The color foreground obtained by Poisson matting is converted to the binary image as reference mask. According to principles of wavelet, we construct watermark embedding function and accurately embed watermark in the interior of ROI. Exploiting watermark extraction function, we extract the watermark from watermarked image. Differentiating the values between embedding watermark and extracted watermark can detect whether ROI of image was tampered, and where was tampered. Experiment results have demonstrated that the presented watermarking scheme can detect tamper in the interior of ROI for image authentication.