本文主要是以模態疊加法(mode superposition method)來分析車橋互制(vehicle—bridge interaction)的現象，在文中主要針對單跨橋和二、三跨連續橋來做分析;並建立列車模型，進而推導整理車橋互制方程式(vehicle-bridge interaction eq.)，其次引入一正弦函數;模擬橋樑軌道面凹凸，最後透過Runge-Kutta Method做數值分析，探討車橋之振動反應。 本文之優點:相較於有限元素法，本文所採之方法較具彈性與準確性;本文之缺點:只能分析定速問題。 In this paper using mode superposition method to analyize the phenomena of vehicle-bridge interaction. Now that we discuss the vehicle-bridge interaction. At first we should make a dicision on the models of bridge and vehicle. There,we aim at single-span bridge , 2 and 3 multi-span bridge. Besides we induct a sine function in order to model the roughness of the orbits which are on the bridge. After reorganizing we will get vehicle-bridge eq. At last we can discuss the vibration between the vehicle and bridge through Runge-Kutta Method ;One of the neumerical methods. Comparing to FEM the method chosen here is more flexibility and reliability. However，my program can analyze const velocity problem only.