Abstract: A simplified model was developed to estimate the seismic response of frame-core tube structures with EDS(energy-dissipation story). In the simplified model, EDS was considered as stiffness spring and damping spring. In order to derive the vibration equation, Heaviside function was constructed by means of modal function and according to the assumed mode shape method and the principle of virtual work. The vibration equation of a frame-core tube structure with EDS was built in MATLAB program, and the mathematical structural model was verified through a comparison with the finite element result in ETABS program. The results show that the proposed simplified model of frame-core tube structure with EDS is valid and feasible. Then the energy dissipation mechanism of frame-core tube structure with EDS could be revealed by explicit expression of vibration equation. Structural damping ratio changing with EDS position could be determined by the complex modal analysis method. Finally, the optimization design for both the complex modal damping ratio and the damping coefficient of viscous damper could be used in the preliminary design of frame-core tube structure with EDS.