In this paper, we study a ring gymnastic robot, which is a planar robot with three links moving in the vertical plane with only the last joint activated. First, we use the energy-based strategy to study the swing-up control task of the rings gymnastic robot, and obtain the sufficient and necessary condition for non-existence of singularities in the energy-based controller. Second, we derive the invariant set approached by the closed-loop system. Third, we propose an optimization algorithm to obtain the parameters of the energy-based controller to swing up the rings gymnastic robot into a close neighbourhood of a desired equilibrium point. Fourth, we check on the feasibility of the devised controller and parameter optimization algorithm through simulation.