With the rapid development of computer networks and the further progress of multimedia technologies,copyright protection of digital media has been one of the most important issues in information technology field. An approach for transparent image watermark based on wavelet multiresolution decomposition is proposed in which a binary image is embedded in the original image. The method uses the characterastic of Human Visual System(HVS) to adjust the intensity of the watermark adaptively. A flag matrix is set to record information about embedding watermark and be used for detecting the watermark. Experimental results show that the watermark is invisible and the algorithm is robust to common image processing.