We describe a novel navigation sensor used for real-time navigation in which a position-sensitive detector is used. According to the features of the position-sensitive detector, the special floor mark stuck on the predefined path is developed. In addition, the formulas for the centroid position of the image of incident laser line on the position- sensitive detector, which is determined by the relative position between the floor mark and the navigation sensor, are derived. The navigation sensor, which can obtain proper navigation accuracy and controlling signal, navigates the autonomous guide vehicle running on the predefined path. It is suitable for application in autonomous guide vehicles and other automatic instruments. The experimental results are given.