This paper describes indoor mobile robot covering path to avoid obstacle based on behavior fuzzy controller. The robot measures the distance to obstacle with ultrasonic sensors and infrared range sensors, and the distance is the input parameter of the behavior-based fuzzy controller. The behavior architecture has three levels behaviors: emergency behavior, obstacle avoidance behavior, and task oriented behavior. The task oriented behavior is the highest level behavior, and has two subtasks: wall following and path covering. The middle level behavior is obstacle avoidance. The lowest level is an emergency behavior, which is the highest priority behavior. The simulation result demonstrates that each behavior works correctly.