An H∞ cont roller for an active suspension system is designed, which has taken the performance of ride comfort and the system robustness into account. Simulation results show that a concentrated weighting of the car body acceleration output, for the frequency w here human being are most sensitive to vibration, has been executed by introducing the frequency dependent weighing function, thus the suspension acceleration frequency response characteristic can be imp roved. It is also pointed out that the designed cont roller is effective in the system robust ness against the fluctuation of parameter of system.