Overshoot and long settling time are two common problems of the positioning control for robotic arms. To solve the positioning control problems, an innovative variable stiffness and variable damping (VSVD) magnetorheological (MR) actuation system for robotic arms was designed, prototyped and evaluated in this paper. The system can reduce the overshoot and settling time of the robotic arm with less energy consumption by controlling the stiffness and damping of its VSVD unit. A robotic arm with the VSVD actuation system was developed and prototyped. In order to evaluate the performance of the system, a step route and a customised route were designed for the robotic arm system to trace. Under these two routes, the positioning control performances of the VSVD robotic arm were evaluated numerically and experimentally with the control modes of uncontrolled, VD, VS and VSVD, respectively. Both the numerical and experimental results demonstrated that the VSVD control mode works best in general with less overshoot, settling time and energy consumption, indicating that the proposed VSVD actuation system can serve as a good candidate to solve the positioning control problems of robotic arms.