Abstract: According to the features of vibration response of hydro-pneumatic balanced suspension, the method to design external characteristics of adjustable damping valve of suspension was put forward. The parameters of three-grade damping external characteristics were designed based on Taguchi method. The external characteristics of shock absorber were optimized to improve the transient response characteristic, riding and wheel ground adhesion index. The designed results indicate that, under stiff damping condition, the handling and start-up comfort of vehicle are acceptable in comfort by designing the damping coefficient at low frequency properly. In addition, the performance of suspension is more robust.