Abstract: Aiming at the problem of structural shock responses in an infinite fluid, a structural response analysis method is established based on the PWA (plane wave approximation) total field formulation and the SBFEM (scaled boundary finite element method) total field formulation coupled with FEM (finite element method). This method uses the PWA total field formulation and the SBFEM total field formulation to simulate the infinite domain, and the FEM equation simulates the underwater structure. By coupling them, the PWA-FEM total field formulation and the SBFEM-FEM total field formulation are established. Through numerical examples, the influences of the number of elements in circular direction, the size and shape of the infinite field truncation boundary on the calculation accuracy of the total field formulation are discussed, and the calculation accuracy of the PWA-FEM total field formulation and that of the SBFEM-FEM total field formulation are compared. The numerical results show the feasibility and accuracy of the total field formulation for simulating the problem of structural shock responses in an infinite fluid. When the SBFEM-FEM total field formulation simulates the infinite domain, it can effectively reduce the discrete range of the finite domain, the requirements for the shape of the truncated boundary are not high, and the scope of application is wider. It provides an effective and feasible solution for the structural responses to underwater shock.