In order to meet the requirements of agricultural production automation, a PC-based opening navigation system for agricultural machinery is designed, which is composed of PC, data acquisition cards, electromagnetic induction sensors, high-frequency electromagnetic generator, DC servo motor and mechanical part. The track of the mobile platform is led by a wire with high-frequency currents laid under the field. The position can be determined by a pair of electromagnetic induction sensors installed in the machine. The traveling path is planed by computer according to information of electromagnetic induction sensor and automatic walking of agricultural machinery is achieved. Based on Visual C + + 6.0 platform, a system software is developed and human-computer interface with good interaction is designed. The results show that, straight navigation accuracy is ± 1.5cm within 10m; the navigation accuracy is ± 3cm when the turning radius is 0.5m. Experiments explain that the system owns high real-time performance and dependability, and that it has a good application prospect.