The calculation of the rigid coupling coefficient matrix of the aircraft is complex and timeconsuming as the finite element method requires operations of data in the highdimensional mass matrix arranged with the element nodes.An optimization algorithm based on non-discrete method is proposed in this paper. The inertia characteristics of flexible components of the threedimensional model could be directly obtained in this calculation, and replace the high-dimensional mass matrix.The error from model discretization could be also avoided. The calculation process is simplified and the accuracy of the calculation results is also improved, which brings convenience in engineering design for the aircraft.