A method, based on the ISO five-class classification for road surface spec trim, to establish the Standardized Road Exciting Spectrum (SRES) on the SITS Road Simulator is presented. These spectrums include the classes of the roughness of road surface and reflect the speeds of vehicles. Through adopting these spectrims the vibration lest for a European made truck has been carried out on the MTS Road Simulator. Through analysing the test data the law of the natural frequency of the system decreasing and the damping increasing in accordance with the intension of exciting signals has been discovered and by means of linear regression of the test data a “system factor” which can represent the characteristic of the transfer function obtained. This enables the vibration analysis of a complex system to become simple. The dynamic characteristic and the transfer characteristic between subsystems of a vehicle can also be assessed by the “system factor”.