A kind of control system modeling and designing method for autonomous following vehicle was provided according to the relative heading angle detected by infrared sensors. The device and working principle of relative heading angle detecting device were introduced in detail. The control system modeling of the steering system driven by a stepper motor, dynamic relationship between front wheel steering angle and relative heading angle, and the corresponding control algorithm design of the whole control system were mainly discussed. The Matlab simulation results of relative heading angle control system were highly consistent with the practical running results of the control system. The autonomous following vehicle system which was modified from electric driven vehicles was tested in an orchard. During the test, the biggest lateral deviation of the tracks between the guiding vehicle and the following vehicle was 9.2cm, the average deviation was 3.3cm and the variance was 5.5cm2. The experimental results showed that the designed autonomous following vehicle system can run stably and reliably, reflected its application prospects in complex agricultural environment.