Abstract: A method for detecting bridge damage is presented on the base of the dynamic response of passing vehicles with uncertain parameters. Based on the train-bridge coupling vibration model and the response sensitivity method, the identified damage indices are solved using the online vibration responses. By computing the sensitivities of the identified damage indices responses to the vehicle parameter, the mathematical expectations and standard deviations of the damage indices can be obtained. Furthermore, the probability estimate of the damage indices can be obtained. The results show that the proposed method is also practical when the uncertainty of vehicle parameters is small; the mass of bogies and wheel-sets, the secondary suspension stiffness and damping have relatively little influence but the mass of car body, the primary suspension stiffness and damping have relatively large influence on the identified result.