In order to study the influence of chamber pressure on thermo-structural response for the submerged nozzle of solid rocket motor, a simulation was carried out. By means of the commercial fluid software, based on the pressure solver, the flow field of pure gas in the nozzle was conducted and the temperature, pressure, and wall convective heat coefficients were obtained in the nozzle; according to the non-uniform pressure and non-uniform heat transfer coefficients obtained from the above flow field, using the finite element software, the thermo-structural problem of the submerged nozzle was solved at the pressure 6 MPa. Then, the ground firing test of solid rocket motor with the submerged nozzle was carried out, and the proposed numerical method is effective and accurate. By means of the same model and numerical method, the thermo-structural response of the submerged nozzle was solved at the pressure 9 MPa and 12 MPa, and the influence of combustion pressure on the thermal stress of throat insert was obtained. The simulation results show that during the entire operation process of solid rocket motor, the maximum hoop stress of throat insert is 103.9 MPa, which locates on the inner surface, and increases at first and then decreases with time; the hoop tensile stress increases at first and then decreases with the increasing of time for the throat insert, as well; with the increasing of pressure, the convective heat coefficients, the temperature and the hoop tensile stress increases, and the hoop compressive stress decreases for the throat insert.