Abstract: A nonlinear coupling model of wheel and rail was established according to the mechanical characteristic of ballastless track with elastic supporting block and the actual parameters of metro vehicle. The time-variant vertical acceleration of the rail and the sleepers can be calculated from the model， and the frequency-dependent acceleration was verified by the fast Fourier transform algorithm. A vibration power fixed by human sensitivity was introduced to quantify the vibration energy of the rail and sleepers. The impact of the parameters in the model was evaluated. The result shows the vibration energy is reduced with the increase of the stiffness and damp， meanwhile， the decrease in amplitude of the vibration energy that is resultant from the increase of the system stiffness is more prominent.

Key words: ballastless track, vibration reduction, wheel-rail couple model, vibration power index, modal method