Existing active control methods for reducing the seismological response of building structures, such as those of linear quadratic optimal control (LQR), have shortcomings in guaranteeing the robust stability and performance of the closed-loop system in the presence of parameter uncertainties. A robust H∞ control approach is thus proposed, which provides a convenient design procedure for active controllers to facilitate practical implementations of control systems, by using a quadratic performance index and an efficient solution procedure based on linear matrix inequalities (LMI). In view of the uncertainty of seismic disturbance and the non-symmetrical shape of the building structure, a multiple degrees of freedom (MDOF) eccentric building with two active mass damper (AMD) systems in the orthogonal direction of the top story subjected to bi-directional ground motions is analyzed. In the simulation, the active control forces of the AMD systems are designed by the robust H∞ control algorithm, and the structural system uncertainties are assumed in the model errors and seismic disturbance. The simulation results demonstrate that the performance of robust H∞ controllers is remarkable and robust, and the efficiency of the control approach is also confirmed. Therefore, the robust H∞ control method is quite promising for practical implementations of active control systems on seismically excited structures.