Abstract: Abstract： Objectives To address the problem of solving two-way strong fluid-structure interaction (FSI) in water impact of marine structures, an efficient and accurate impact load prediction method is proposed. Methods In the open-source computational fluid dynamics library OpenFOAM, based on the partitioned two-way coupling theory, a two-way FSI calculation method coupling the Finite Volume Method (FVM) and modal superposition for impact load prediction is proposed. The computational performance of this method is systematically verified through a two-dimensional dam-break impact test on a flat plate and a water slamming test on an elastic wedge with a 20° deadrise angle, and the influence of dynamic and kinematic effects on calculation accuracy under significant elastic effects is analyzed. Results The calculation results of this method show good agreement with experimental data: for the two-dimensional dam-break impact on the flat plate, the calculation error of the maximum impact deformation at the plate top is about 7%; for the water slamming of the elastic wedge, the calculation error of the peak slamming pressure is about 2%, and the calculation error of the peak stress ranges from 5% to 12%. Conclusions The proposed impact load calculation method coupling finite volume and modal superposition demonstrates good calculation accuracy and reliability, meeting the requirements of practical engineering applications; for impact problems with significant elastic effects, it is imperative to consider the influence of dynamic and kinematic effects when calculating nodal loads in the fluid domain during FSI solution.