在研究U系统的基础上，提出了一种在图象中植入数字水印的简便易行的方法，介绍了分段线性U系统及其性质，并将其扩展为分段K次U系统；在讨论如何使用分段线性U系统对数字图象进行分 的基础上，提出了基于U系统的数字图象水印方法，并给出了相应的实验结果，实验表明这种算法是可行的。

This paper present a novel easy and effective algorithm to plant digital watermark into digital images, this algorithm is different to general watermarking methods based on spread spectrum, because a new orthogonal base based on piecewise polynomial is constructed. The watermark based on this algorithm can resist energy loss caused by lose compression of digital image. In the first part of this pper, piecewise linear U system and its properties will be introduced respectively, corresponding graphs are shown, too. Following this part, how to generalize this algorithm to piecewise k degree U system is discussed; In the third part fo this paper, based on decompose digital image by piecewise linear U system, a kind of digital image watermarking scheme will be provided, the process of this algorithm is introduced step by step. By the end of this paper, some corresponding experimental results based on U system will be listed. The experimental results demonstrate the algorithm is reliable.