Steering wheel angle detection is one of the key technologies to realize automatic navigation of agricultural machinery. The measurement results of agricultural machinery steering wheel angle directly affect the accuracy of automatic navigation control and the effect of agricultural machinery operation. Taking the Lovol M904-D wheeled tractor as the research platform, the WYH-3 noncontact angle sensor was used to study the calibration and detection method of steering wheel angle of wheeled tractor. The installation method of tractor steering wheel angle sensor was introduced. The relationship between angle sensor and agricultural machine steering angle was calibrated by scaled dial. The calibration results showed that the correlation was significantly and the coefficient was over 0.99. Focusing on the bias error in the wheel angle calibration test, a curve optimization fitting method based on the least squares principle was proposed to estimate the position deviation of the wheel relative to 0°. Preview tracking model based path tracking test showed that the extreme value of navigation control deviation was 2.74cm, the average absolute value of deviation was 0.49cm, and the standard deviation was 0.58cm. It indicated that the path tracking control precision was high, and the feasibility and accuracy of the steering wheel angle detection scheme were verified. 