This paper first describes key conceptions about object oriented analysis in software engineering, behavior based robotics and their conceptual similarities. Then, based on these similarities, the paper utilizes object oriented methods of software engineering, such as unified modeling language (UML), to analyze and model the architecture and design behaviors for a behavior-based robot, which is expected to wander with autonomous obstacle avoidance in unknown environment. Object oriented methods permit a translation from conceptual behavior models to computer programming representations, and separate concrete control algorithms from robot modeling. With this approach, the paper also implements a fuzzy algorithm for obstacle avoidance behavior of the constructed behavior models in a physical robot. Finally the paper gives experimental results and points out future directions.