In order to control excavator automatically, an excavator was retrofitted with electro-hydraulic proportional control systems. Kinematic models for excavator’s mechanism and nonlinear model for its electro-hydraulic system was established respectively. The dead-band and asymmetry nonlinearities of the electro-hydraulic system which was deduced in the theory models was demonstrated by experiments. To satisfy ground-leveling task, a 5-order polynomial was used for path generation in Cartesian space, and the joint-space path was calculated by kinematic models. According to the dead-band and asymmetry nonlinearities of control system, a segment PID controller with dead-band compensation was designed. Comparison experiments demonstrated that segment PID overcame the majority nonlinearities effectively. It had better tracking performance than conventional PID. In conclusion, complex path tracking was achieved by coordinated control of the three working arms. 