Abstract: The ocean environment is always uncertain, unstructured and unknown. Furthermore, the obstacle avoidance sonars of long distance AUV (LAUV) only have restricted abilities to get environmental information. These facts make it very difficult to build a precise, complete and general 3 dimension model for ocean environment. Real time Obstacle Avoidance (ROA) of LAUV is a dynamic process with distinct real time characteristics. It is related to ocean environment, as well as kinematics restriction, dynamics and maneuver. To solve these problems, a fuzzy obstacle avoidance algorithm based on complex control strategy is presented in this paper.