Abstract: To explore the random characteristics of the derailment coefficient safety index of high-speed railway trains, the random vibration model of a vehicle bridge is established by multi-body dynamics theory and finite element method based on the pseudo excitation method (PEM) and extreme value theory. A vertical wheel/rail corresponding and lateral linear creeping wheel-rail relationship is used to build the dynamic equation of the train-bridge coupling system. The track irregularity is transformed into the superposition of harmonic loads at a series of frequencies by the pseudo excitation method so that the non-stationary problem is changed into a deterministic time history problem. The power spectra of the wheel-rail force are obtained by the separate iteration method. Based on the modulation function, the harmonic superposition method is used to add the wheel rail force at each time to obtain the wheel rail force time history sample. The probability distribution function of the maximum derailment coefficient is explored by the extreme value theory and its maximum value is obtained. The stationary characteristics of the wheel rail force power spectrum under different defection span ratios are discussed. Taking a 24.6-meter simply supported concrete beam as an example, we fitted the extreme value distribution of the derailment coefficient under various vehicle speeds. The results show that the extreme value distribution can well fit the extreme value of the derailment coefficient under different speeds. The higher the speed, the stronger the discrete type of the extreme value distribution of derailment coefficient, and the larger the derailment coefficient value corresponding to 99.73% confidence level, which is greater than the maximum of time-domain samples. In the analysis cases, the bridge deformation has little influence on the stationary characteristics of the power spectra of the wheel rail force.