Abstract: This paper proposes a variable structure control scheme for robot tracking control in the operational space. The control algorithm of the proposed scheme does not require the conventional coordinate transformation from the Cartesian space to the joint space as the joint torques are computed directly upon the desired trajectories specified in the operational space so that it is time efficient and not prone to the singularity problem. The fundamental idea of this paper is to find a simple swithing law that can be predetermined according to the bounds of the parameter uncertainties off-line, and execute the law on-line to achieve a real time variable structure control.