Abstract: One of methods to improve the computational efficient in the analysis of a large-scale structure is to take the existing finite element part models of the design stage as substructures. As a result,the meshes of these substructures are likely to be incompatible at their interfaces. In traditional methods,complex interface elements are necessary to ensure the deformation compatibility. We presented a new method of joining such substructures without recourse to the interface element,which facilitate the cooperation among departments involved in the structure design. With the presented method,displacements of nodes on the interface can be also eliminated from equilibrium equations during the procedure of joining two substructures,and consequently improves the computational efficient further. Finally,the presented method is verified by a numerical example.