Abstract: Combined with the scaled boundary polyhedron finite element analysis method, this paper firstly applies the Octree Technique to the nuclear engineering. The refined damage evolution analysis of large commercial aircraft crashing into Generation Ⅲ+ nuclear power plants is developed. Meanwhile, the influence of foundation effect, shape of impact region chosen and SSI effect is discussed. The results indicate that the cross-scale refined analysis method is with extremely strong capability of discrete grid, high quality and little quantity of element. Furthermore, the method is highly flexible for the model modification; the refined FEM model simulates more accurately the damage evolution and gradually destruction process; the structure-soil interaction (SSI) effect in the analysis of the aircraft impact on nuclear islands cannot be ignored in non-lithology foundation.