Abstract: Research purposes: The excessive bridge vibration caused by train will affect the safety of train running when it is crossing the bridge. In order to ensure the safety and steady, a train - bridge coupling random vibration model need to be built and the bridge dynamic performance should be analyzed. Based on the space time varying train - bridge coupling system model and track irregularity power spectrum， this paper designed a train - bridge coupled random vibration analysis program by using MATLAB，calculated the standard deviation value for the random response of the train - bridge system by adopting pseudo excitation method. Research conclusions: (1) Compared with the Monte Carlo method, the pseudo excitation method is a simple and rapid way in working out the standard deviation value and response power spectrum. It has higher accuracy and computation efficiency by 1 ?2 order of magnitudes. (2) The range of the random vibration response was obtained by using the theory of triple standard deviation，and the paper compared it with the existing specification limits, provided a new thought for the bridge dynamic security analysis. (3 ) The maximum value and minimum value curves of the lateral acceleration and amplitude are symmetrical and most random. As to the vertical acceleration, the deterministic part of the response is as important as the standard deviation caused by the track irregularity. (4) The vertical displacement is of less randomness and mainly determined by the determined loads. (5) The result provides a scientific basis for bridge dynamic performance evaluation of train - bridge coupling random vibration.