Abstract: A new method is presented and proposed to settle the problem, easy but not to be neglected, existing in the current displacement input model for the seismic-responses analysis of multi-degree-of-freedom multi-supported structures subjected to spatially ground motion. The method is called appended massless rigid element method. Firstly, the current displacement input model is reviewed, and the unnegligible problem inherent in it is described in detail. To solve the problem, the spring impedance method is presented. Then, the rationality and accuracy of the proposed method are further verified. Moreover, the method is applied to bridge engineering. Theoretical analysis and numerical results demonstrate that the proposed method is not only has the characteristics of explicit physical meaning, simplicity and feasibility, but also compared with the AMCE method in the previous literature. It avoids constraint condition and does not require additional improvement or subprogram for existing general finite element program. So, appended massless rigid element method is more realistic and is worthy to be generalized.