Traditional raft foundation designs for nuclear power plants and civil buildings are mostly based on the theory of linear elastic boundaries. Civil buildings are mostly based on one-dimensional linear elastic boundaries, while nuclear power plant designs are based on three-dimensional linear elastic boundaries. However, in reality, foundations generally exhibit nonlinear characteristics, and traditional methods have not fully considered that. This article takes the common raft foundation of a third-generation nuclear power plant as the analysis object, and uses high-order solid elements to study the transient temperature field under high-temperature accidents and shrinkage creep effects in the analysis of raft foundations. Based on this, nonlinear boundary conditions are proposed, and the introduction of nonlinear boundaries improves the economic efficiency of the common raft foundation design. At the same time, an equivalent damping coefficient was introduced for the foundation boundary under earthquake conditions, and the “super element” method was used for seismic load analysis, which greatly improved the calculation efficiency while ensuring calculation accuracy.