This paper presents an obstacle avoidance control algorithm for mobile robot based on fuzzy controller. The environment information surrounding the robot detected by the ultrasonic sensors is firstly fuzzified, and then input into fuzzy control system. The output of the fuzzy control system is used to drive the robot. And the fuzzy control system in this paper is composed of dual fuzzy controllers, one is used to control the obstacle avoiding behavior when the robot is approaching obstacles, otherwise the other controls the robot to move to the goal. In this paper, the design of obstacle avoidance controller is described in detail, and the both are implemented by matlab. In order to obtain control information, it's necessary to fuse the output information of the two controllers. At last, simulation results show that the algorithm can help the robot to avoid obstacles safely and is certainly feasible.