本文用桥梁结构动力学和车辆动力学的研究方法，从轮轨力、脱轨系数和轮重减载率着手，对列车过桥脱轨原因进行了研究。并以秦沈客运专线的桥梁为例进行了计算。

Based on the study method about bridge structure dynamics and vehicle dynamics, this paper studies the reasons of train derailing on the high-speed railway bridge, such as the wheel-rail force, the derailment coefficient and the load decrement rate of wheel weight. By the example of the bridge on the Qin-Shen special passenger traffic railway line, the calculation has been put forward.