This paper introduces a new method which is based on multi-body hydrodynamics and Euler–Bernoulli beam assumption to study hydroelastic behaviours of very large floating structures (VLFSs). A continuous VLFS is divided into several modules, being multi-module floating structures. The section between two adjacent modules’ centre is seen as a beam element. Based on the above assumption, the six-degree-of-freedom motion of a module's centre is both affected by the hydrodynamic interaction with its adjacent module and restricted by the deformation condition of the equivalent beam between two modules. Then the motion equation of the equivalent multi-module floating structures can be established utilising the potential flow theory and Euler–Bernoulli beam hypothesis. The results calculated by the present method are compared with experimental results and numerically calculated data by three-dimensional hydroelastic theory, which shows rather good agreement.