Abstract: The resonant responses of mega-frame-core-tube structures are analyzed by the semi-analytical method based on ODE (Ordinary Differential Equation) solver, using a continuously distributed mass and stiffness model in space dimension. That is, the mega-frame-core-tube structure and its foundation are simplified equivalently and continuously into a three-dimensional model, a stiffened thin-walled tube-in-tube on a semi-infinite elastic subgrade. The computed results indicate that the model is reasonable and feasible, and a new approach as well as a new dynamic analytical method is developed for the insight into dynamic performance of mega-frame-core-tube structures.