In order to improve the control precision of the autonomous navigation operation of agricultural machinery in farmland environment, three steering wheel turning control systems based on different types of motors were designed and developed. Based on the analysis of the parameters of the three kinds of motors, such as stepper motor, servo motor and stepper servo motor, and their performance differences, the tractor automatic steering actuator was designed, and equipped with industrial computer PC, PLC controller, front wheel angle detection mechanism and GNSS positioning system. The design and development of the industrial vehicle terminal software can realize the automatic navigation nested double closedloop control system and the corresponding PID control algorithm; the electrical schematic of the control system and the PLC steering program were designed. Finally, the tractor automatic navigation concrete pavement and field sowing test were carried out. When the tractor was linearly navigating at a speed of 0.8m/s, under the two test conditions, the root mean square errors of the stepper motor navigation system were 8.81cm and 12.09cm, respectively, the root mean square errors of the servo motor navigation system were 4.85cm and 10.55cm, respectively, and the root mean square errors of the stepper servo motor navigation system were 4.54cm and 5.53cm, respectively. The test results showed that the stepper servo motor had the best performance for steering wheel turning control in the automatic navigation system.