A simulation system for dynamic coupling model of vehicle suspension and roadbed was presented. A low-order model was obtained from the finite element model of the roadbed by the modal truncation method and it was transformed to a state space presented form for applying to simulation model of suspension. The dynamic coupling system under road dis- turbances was simulated on Simulink system. The relations among dynamic tire force, de- formation of road surface, vehicle speed, elasticity of roadbed materials and dynamic stress in road were analyzed.