Abstract: Tsunami is one of the main disasters threatening the safety of coastal bridges. It is of great significance for the coastal bridges to dig into the superstructure-tsunami interaction process, and to study tsunami wave-induced forces on the bridge superstructure and on bridge bearings. In present study, a 2-D numerical wave tank was developed by using the open source software OpenFOAM. The dam-breaking wave was adopted to simulate tsunami waves. The RANS (Reynolds-averaged Navier–Stokes) equations combined with the k-ɛ turbulence model were utilized to describe the mean flow motion. The spring-mass-damper system was utilized to numerically simulate the moving system of the bridge superstructure. The coupling effect between tsunami and bridge superstructure was considered through the real-time data transmission between fluid and spring-mass-damping system. Then the numerical model was verified by the theoretical formulas of dam-breaking wave and the experimental measurements in the pertinent literatures. With that, the influence of the fluid-structure interaction effect and the lateral restraining stiffness on wave force were analyzed. Meanwhile, the stress state of the bridge bearings during tsunami action process was explored. The results indicate that: the numerical model developed is capable of capturing the wave-structure interaction process; after considering the fluid-structure interaction effect, the maximum wave forces on the superstructure decreases significantly. For the horizontal force, the maximum value decreases nearly 16.8%~21.0%, and maximum vertical force decreases nearly 15.5%~19.5%; compared with the horizontal force on the bridge superstructure, the horizontal bearing force fluctuates more obviously and its maximum value reaches 1.25 times of the horizontal force on the superstructure; the bearing at upstream side experiences both tensile and compressive state, and its maximum tensile force exceeds 90% of the maximum vertical force on the superstructure; the bearing at downstream side only experiences compressive state, and its maximum compressive force is about 1.11~1.55 times of the maximum compressive force on the upstream bearing.