Aiming at No. 18 high-speed turnout, a dynamic model of vehicle/turnout rigid-flexible coupling system has been established to analyze wheel/rail interaction when a train passed through turnout at different speeds. By Wigner-Ville distribution based on the time-frequency analysis, the axle-box acceleration (ABA) was further studied. Bending deformation of the flexible wheelset under axle load makes a small constant amplitude vibration of the wheel/rail force and the ABA. When a train passes through a turnout in the main and diverging routes, the long nose rail width around 0.04m and the curved switch rail width around 0.02m receive impacts from the wheel. It leads to the vertical high frequency ABA at around 300Hz which is close to the natural frequency of the wheelset and it's more likely to cause the wheelset compound vibration of symmetrical umbrella and the third order bending mode.