Abstract: The automatic steering control system of SPU-60 rice transplanter was studied in this paper. The control system included steering controller and driving mechanism. Adaptive PD control algorithm was developed for orientation tracking. The orientation error was used as the input parameter of the controller. The output parameter of the controller was the steering angle of front-wheels. Proportional coefficient of the controller could be adjusted automatically according to the velocity. Simulation and experimental results showed that the control algorithm could be used for orientation tracking. Adaptive PD controller has good orientation tracking performance. The automatic steering control system could be the base of trajectory tracking control of wheeled model farming machinery.