Abstract: A new method for a vertical non-stationary random vibration analysis of vehicle-bridge systems subjected to track irregularity excitations is proposed. The vehicle is modeled as a four-wheel mass-spring-damper system with two layers of suspension systems possessing 10 degrees of freedom. The bridge is modeled as an elastic Bernoulli-Euler beam, and the track irregularity is assumed to be a uniformly modulated evolutionary random process with the phase-lags between the wheels taken into account. Pseudo-Excitation Method (PEM) is applied to transform the random surface roughness of the track into the superposition of a series of deterministic pseudo harmonic surface unevenness and thus simplifies the solution of the non-stationary random vibration equations considerably. Meanwhile the Precise Integration Method (PIM) is developed to simulate the continuous varying of the vehicle loads both in the time and space domains in the numerical integration process. Numerical examples are given and the influences of the track irregularity on the system random responses are discussed. Comparisons with the Monte Carlo simulations show the effectiveness and satisfactory accuracy of the proposed method.