Abstract: Non-stationary random vibration and peak value estimation of 3-D train-bridge systems subjected to the action of lateral horizontal earthquake are investigated based on the pseudo-excitation method (PEM). The lateral horizontal earthquake is assumed to be a uniformly modulated non-stationary random process, while the excitations of track irregularity are assumed to be multi-phase uniformly modulated non-stationary random excitations. The pseudo-excitation method is extended and applied to transform the random excitations due to horizontal earthquake and track irregularities into a series of deterministic pseudo harmonic excitations respectively. And then the corresponding pseudo responses are solved by using the precise integration method (PIM) iteratively. By this means, various non-stationary random responses including the time-dependent PSD and RMS of interested quantities can be obtained easily. Furthermore, a new estimation method of peak value for such non-stationary random responses is suggested based on first-passage failure criteria. The effectiveness and accuracy of the proposed method are justified numerically by the time history method, and the influence of site type on random responses of the system is discussed.