As one of the main performance indexes,the vibration of vehicle affects the passenger ride comfort characteristic,the control stability,the endurance life of detail and then the safety of vehicle.Traditional passive suspension has become incapability in waning vibration.In order to improve the capability of waning vibration,the non passive suspension by using electronic control method has been studied in recent years.Based on a quarter model with two freedoms of BJ212,the authors believe that the vehicle suspension system is both controllable and observable by analyzing the controllability and observability and this conclusion could be applied to optimal control and design of non passive suspension.