The two-parameter optimal control method based on the speed and steering angle was designed with the optimal control theory. The automatic transmission system and the automatic steering system were developed for the automatic navigation tractor on the purpose of improving the work efficiency and the work quality. The straight path tracking controller and the turnrow turning path tracking controller were designed and simulated by the harrowing operation with the Matlab. The field test was carried out to validate the designed controller, and the results indicated that the control accuracy of the lateral deviation and the orientation deviation were less than 0.12 m and 1.1°, respectively. The speed control accuracy was less than 0.2m/s. 