In this paper, an efficacious and accurate method for analyzing random vibration and fatigue lifespan of coaches with high degrees of freedom is developed. Based on the design requirements for structure strength and fatigue lifespan of a coach, the finite element model of its body structure was used to investigate the dynamic behavior of the coach running on a randomly uneven road. The vibration characteristic was derived using the pseudo excitation method (PEM). The fatigue lifespan is discussed by means of the Miner rule, and the fatigue resistance is also studied. The reliability of the proposed method is numerically verified.