10cm。An autonomous navigation system based on self-adapted fuzzy control for agricultural tractor was proposed. PLC, electro-hydraulic switch valve and proportional directional control valves were used to construct the automatic steering control system based on PD control algorithm. A self-adapted fuzzy control algorithm was proposed, GA was adopted to optimize the fuzzy rules and proportion factor of fuzzy output online. It retained the advantages of conventional fuzzy control, and meanwhile, it improved the performance of autonomous navigation control system. Simulation and field experiment indicated that the proposed navigation control algorithm could eliminate the tracking error effectively with rapid response and small overshoot, the navigation system worked stably, the maximum tracking error was less than 10cm.