Abstract: With the track, bridge and its piers taken as an integrated system, the finite element model to analyze the additional longitudinal forces in continuously welded rails (CWR) on bridges was established. The distribution of additional longitudinal forces due to temperature and bridge flexure and the influences of braking forces and the forces due to rail breaking were studied. The results by simulation conform with the principle of CWR on bridges. A simulation program named BCWR is presented, which can be applied to the design of CWR on supper-large bridges of high-speed railways.