Abstract:  The selection of seismic motion input methods in artificial boundary conditions directly affects the accuracy of numerical simulations. However, existing research still lacks systematic comparisons of different input methods at the boundaries of three-dimensional (3D) sites. This paper focuses on 3D homogeneous half-space and layered half-space sites under plane SV wave incidence. Based on the Multi-Transmitting Formula (MTF) theoretical framework and combined with the APDL parametric modeling technology of ANSYS finite element software, the computational accuracy of site seismic responses under three reference wavefield input methods is compared and analyzed: (1) Inputting the free wavefield at the front, back, and left side boundaries of the computational model, the incident wavefield at the bottom boundary, and no wavefield input at the right side boundary. (2) Inputting the free wavefield at the left, right, front, and back boundaries, and the incident wavefield at the bottom boundary. (3) Inputting the free wavefield at the left, right, front, back, and bottom boundaries. The results show that the error between the seismic response of the 3D site using method (3) and the theoretical solution is the smallest, significantly outperforming the other two methods.