Most of the nuclear power plants are built around the coastal or along the rivers. Below the underground water level， dis? tribution of the water in the soil pore has a great influence on the seismic response of soil， which affects the response of the nuclear power plants. To analyze the effect of the underground water level on the seismic response of nuclear power plant， a saturated po? rous medium model considering the interaction of the saturated soil and structure is used in this paper. Firstly， the free field of the horizontal layered site of dry soil-saturated soil is obtained by the transfer matrix method， and the wave input of soil-structure inter? action analysis is realized combined with the transmission boundary； Then， the partitioned parallel calculation method of soil-struc? ture interaction is used to analyze the saturated soil-structure interaction. The soil with groundwater level is described by the gener? alized saturated porous medium model which is simulated by the lumped-mass explicit finite element combined with the transmis? sion boundary using the self-programmed FORTRAN code， and the structure is analyzed by ANSYS using implicit finite element. Taking a nuclear power plant as an example， the dynamic response of soil-base-nuclear power plant system is analyzed in five sites with different groundwater levels of -10 m，-20 m，-30 m and -40 m， as well as pure saturated soil. The results show that the groundwater level has a great influence on the response of foundation and structure. For the calculation example in this paper， the results show that the groundwater level has little effect on the displacement of the foundation and structure， but has a great ef? fect on the acceleration of the foundation and structure.