Abstract: A H∞ control method based on acceleration feedback of complex large-scale structures is presented. Since complex large-scale structures generally involve excessive degrees of freedom, a controller design based on a full-order system may be difficult. A reduced-order control method has thusly been adopted. The reduced-order H∞ controller and H∞ observer are designed by combining a balanced reduction method and H∞ control algorithm using absolute acceleration information measured by acceleration sensors located on the base. The numerical simulation is performed on ATMD active control of seismic responses of a jacket platform to evaluate the effectiveness of the presented method and to identify the optimal parameters of controllers. Simulation results show that the seismic response of the platform can be considerably reduced if the parameters of the reduced-order H∞ controller are selected appropriately.