Abstract: This paper discusses how to recognize and locate pipeline accurately by vision in underwater environment. An underwater vision system is presented. The object′s color is the feature when the object be recognized. And the color is transformed from RGB space to HSI space, which improves speed of image processing and robustness of feature extraction. Because the illumination of underwater environment changes tempestuously, fuzzy network is used to adjust threshold value of feature color dynamically. The paper analyzes location of point and line in underwater environment in detail, and offers an algorithm of location. Experiment results show that the method can achieve quite precise location effectiveness.