Abstract: The dynamic stability of subgrade in transition zones has become a key problem restricting the design of high-speed railway subgrade with a speed of 400 km/h and above. It urgent to explore the amplification mechanism of system dynamic response caused by non-uniform foundation from the perspective of wave and energy. Based on this background, this paper combines the transition radiation theory and considers the complex propagation of radiation waves between interfaces, proposing a solution method for the transition radiation wave field in multi-interface elastic layer under moving load. This model can be used to simulate and analyze the additional displacement and energy distribution directly caused by the non-uniform stiffness of the subtrack foundation of the transition zones, revealing the inherent mechanism of the amplification of dynamic response in the transition section with the increase of load velocity. The results show that as the load velocity continues to increase, the additional displacement and energy of the sub-track foundation increase continuously and the growth rate becomes larger and larger. When approaching the critical speed, from 120 m/s (432 km/h) to 130 m/s (468 km/h), the peak increase in additional displacement is 119.49%. The proportion of additional displacement in the total displacement at the same time has increased to 45.88%, which indicates that additional displacement has become the main risk source for controlling deformation. On the other hand, the peak increase in additional energy (transition radiation energy) was the highest at 604%. In addition, the ratio of total transit radiation energy to total strain energy increases to 43.55%, indicating that the additional energy caused by non-uniform changes in the stiffness of the sub-track foundation has become an important part of the overall system energy distribution, posing challenges to deformation control and long-term service performance maintenance in the transition zones of high-speed railway.