Applying the compressibility of air, the vibration transmissibility can be reduced by the passive pneumatic vibration isolator, but the vibration amplitude in the low frequency is still not decreased, even having resonance. Using active pneumatic vibration isolator the disadvantage of the passive system can be improved. The mathematical model of the pneumatic vibration isolator is built up and the characteristics of the effecting parameter are defined. Using off line method to identify the active valve controlled system, and design the adaptive controller to control the vibration isolator. The experiments show that the vibration amplitude of passive pneumatic vibration isolator in the low frequency can be decreased by active control.