A navigation control system for agricultural machinery was developed based on CAN bus with the communication protocol of ISO 11783, which was the standardization for the exchange of information between different devices in the system. The system includes a control terminal, an acquisition unit of GPS signal, an acquisition unit of digital compass signal, an acquisition unit of angle sensor signal, and a steering control unit. A self-adaptive PID algorithm was adopted to perform steering control. The communication experiment proved the effectiveness of the system in collecting data and transmitting commands. Experimental results showed that the algorithm could quickly track target datum, and made the system have better dynamic response characteristics.