Abstract: A three-dimensional numerical analytical method in time domain for the soil-spatial structure dynamic interaction is proposed. The spatial structure is modeled by ANSYS software, and the unbounded soil is modeled by the lumped-mass finite element and transmitting boundary. The three-dimensional integral model that includes the soil, foundation and spatial structure is developed. The explicit-implicit integration scheme is used, and the efficiency can be greatly improved by using different time steps in the soil and structural analysis. The nonlinear influence of spatial structures can be taken into account in ANSYS software. A lumped mass model and a four-point-supported square pyramid space grid are researched and the results confirm the feasibility and validity of the method.