Abstract: With the methods of bridge structural dynamics and vehicle dynamics, regarding high-speed trains and the long span cable-stayed bridge crossing over Yangtze river at Nanjing in Beijing-Shanghai high-speed railway as a combined vibration system, the 3-dimensional coupling vibration responses of the train and bridge are analyzed. The influences of the train speed on bridge deflection, vehicle comfort quality and safety quality are studied. Results show that, though the ratio of deflection-to-span under 0.8 UIC load is 1/600, high speed trains can pass itwith satisfactory safety and comfort.