Abstract: To implement the trajectory tracking control of a robotic excavator, the 4-DOF Lagrangian dynamic model of a robotic excavator's working device was developed with a robust controller designed. The relevant control law includes an equivalent control and auxiliary control, where the former ensures that the control input of a closed-loop system is based on the expected dynamic model, while the latter ensures the robustness of control system and the tracking error which approximates to zero if there are dynamic modeling errors and uncertainties. The fuzzy control is applied to alleviating the chattering during control input. With the designed fuzzy robust controller used in simulation, its effect of trajectory tracking and control input are both given.