A whole vehicle dynamic model is built, and the modeling method of connected hydragas spring suspension and multi-axle grouping steer system is also explained. Firstly, a kinematical analysis of suspension is implemented to achieve optimized suspension geometry parameters according to the stable requirement. Then, based on the evaluation of whole vehicle handling character with regard to various tire characters, driving configurations and super structures, the design rules are summarized to improve the stability of multi-axle vehicle. A whole vehicle dynamic model is built, and the modeling method of connected hydragas spring suspension and multi-axle grouping steer system is also explained. Firstly, a kinematical analysis of suspension is implemented to achieve optimized suspension geometry parameters according to the stable requirement. Then , based on the evaluation of whole vehicle handling character with regard to various tire characters, driving configurations and super structures, the design rules are improved to the stability of multi-axle vehicle.