This paper develops a practical approach based on Python that couples the hydrodynamic analysis with the structural analysis, in order to solve the hydroelastic problem of Very Large Floating Structure (VLFS). The hydrodynamic analysis is carried out by solving linear 3D diffraction and radiation problems in the frequency domain, while the structural analysis is performed by a time-domain nonlinear finite element model. The coupling is realized by a generalized mode expansion method where the elastic deformation of the VLFS is regarded as extended radiation mode in the water. We consider a pontoon-type floating plate in regular waves. Analytical mode shape functions are used for representing the VLFS elastic deformations. The Mindlin plate theory is used for the finite element model. Convergence study of structure mode shape numbers, hydrodynamic model mesh and finite element model mesh is carefully carried out. Good agreements of the vertical displacement of the floating plate are found compared with experimental data and numerical results in the literature. Our simulation results show that the dynamic response of the VLFS is significantly influenced with consideration of its elastic deformation in the waves, and we see the influence is more pronounced in relatively shorter waves. The proposed approach is shown promising for hydroelastic analysis for more complex VLFS in realistic ocean seastates.