The performance of active suspension is considered to be better than that of passive suspension. A 2degree of freedom model of quarter car active suspension system was designed, which is subject to road disturbance. A robust control scheme was proposed for input with unknown nonlinear dead zone. The controller can eliminate the residual vibration caused by the inaccurate parameters. H∞ controller improves vehicle ride comfort and handling capabilities as well as system robustness. The simulation results show that the H∞ controller is robust to the uncertainty of system parameters. It can effectively reduce the harmful influence of the dead zone on the system, control unpredictable interference within the input range, and provide overall stability of the active suspension.