The dynamic response computation and fatigue life prediction of the vehicle systems under random road spectrum are important topics in modern vehicle truck design. In this paper a seven-degree-of-freedom (7-DOF) model of the car was developed. This model was used to calculate acceleration power spectral density of the car systems and study the response characteristics of drive axle housing under the action of random road spectrum and analyze the resonant frequency zone on the basis of the acceleration power spectral density of the rear-wheel. Furthermore, the dynamic stress of the drive axle housing was calculated with finite element method. The result was applied to predict the fatigue life of the drive axle housing by using ANSYS Workbench and Miner's cumulative-damage law. The method developed in this work is not only suitable for the running dynamic structure but also suitable for simulation computation that the new dynamic structures will be designed especially. © 2012 American Scientific Publishers All rights reserved.