Electromagnetically inductive navigation system of the spraying robot is developed to meet the requirements of automatic spraying operation. The system is composed of the mechanical part, electromagnetic inductive sensor, SCM-based control system and DC electromotor PWM drive system. The mathematical model constituted by integral element and inertia element is founded with the DC servo-motor voltage as the input variable through the structural analysis of the navigation system. The increment digital PID algorithm is applied to achieve running path control of the spraying robot. Experimental results indicate that the spraying robot navigation system based on digital PID algorithm overcomes time-varying volatility, nonlinearity and strong coupling, thus has fast response speed and good robustness.