This paper describes a numerical simulation technique that is used to investigate the dynamic train/track/bridge interaction. Two dynamic models are established to simulate the dynamic responses of a train running on the bridges with the ballasted track and the non-ballasted slab track, respectively. Effect of the track structure and the wheel/rail interaction on the system dynamics is considered in the models. The nfluence of track random irregularities on train/track/bridge dynamic interactions is investigated. The proposed simulation technique is applied to practical construction engineering in the Chinese first special railway line for passenger transport. The structural design of three extraordinary large bridges with non-ballasted tracks in this line is evaluated through a detailed simulation in the design stage and results show that these bridges are able to satisfy the demand of dynamic performance for the high-speed transport.