Abstract: Digital watermarking is a new research topic about copyright protection in recent years. Watermarking is a technique for labeling digital picture by hidding secret information in the images. Sophisticated watermark embedding is a potential method to discourage unauthorized copying or attacking the images. This paper presents a technique of watermark embedding and extracting based on discrete wavelet transform of blocks in the image. Each pixel of a watermark is embedded in the wavelet coefficient of the middle and low frequency of a block in the images. Disputation about copyright can be settled down by using the watermark embedding technique presented in this paper. Both theoretical analysis and experimental results show that this technique is reasonable and satisfactory.