This paper presents a robust hybrid control system for seismic response control of a cable-stayed bridge. Because multiple control devices are operating, a hybrid control system could alleviate some of restirctions and limitations that exist when each system is acting alone. A LQG algorithm with on-off control scheme, H2 and H$_{\infty}$ control algorithms with various frequency weighting filters are used to improve the controller robustness of the active control part in the hybrid control system. The numerital simulation results show that control performances of robust hybrid control systems are similar to those of the hybrid control system with LQG algorithm. Furthermore, it is verified that robust hybrid control systems are more robust than the hybrid control system with LQG algorithm and there are no signs of instabilities in the ±5% stiffness matrix perturbed system. Therefore, the proposed hybrid control system have a good robustness for stiffness matrix perturbation without loss of control effectiveness.