Abstract: In order to investigate the dynamic responses of a high-speed train under earthquake and the effect of spectrum characteristics of seismic wave on high-speed railway vehicle derailment, a coupling vehicle/track dynamic model with an earthquake excitation is put forward, in which the vehicle is modelled as a 35 DOF multi-body system with nonlinear suspension characteristic and the slab track is modelled as a discrete elastic support model, which consists of rails fasteners, track slabs and a Cement Asphalt Mortar layer. Rails are assumed to be Timoshenko beams supported by discrete rail fasteners, and the slabs are modelled as solid finite elements. A moving track support model is used to simulate the effect of the periodical discrete track supports on the vehicle/track interaction, and the earthquake motions are simplified as cyclic lateral sine waves for the boundary input of the coupling vehicle-track system. The detailed numerical simulation makes an investigation into the dynamic behaviour of a high-speed railway vehicle excited by the earthquake excitation, and focuses on analyzing the effect of seismic wave spectrum on derailment mechanism of a high-speed vehicle. Through the numerical analysis, it is found that the spectrum characteristics of seismic wave have a great effect on the dynamic responses and derailment mechanism, also the operation safety of a high-speed railway vehicle.