Considering the coupling effect of vehicle body vertical and pitch motions during driving，the contact force of the two-axle four-degree-of-freedom vehicle dynamics model during crossing the bridge are derived from the body response，and the response sensitivity method and regularization technique are employed to identify the bridge structural damage. The numerical study results reveal that，with the road roughness taken into consideration，compared with the methods using the sensitivity of vehicle body or wheel-axle responses，the method using sensitivity of contact force has a better damage detection accuracy. Compared with the damage identification using contact force sensitivity of a single axle vehicle，the proposed method could reduce the iteration number significantly. The parametric study results indicate that the damage identification accuracy is affected by vehicle speed，noise，and model error. The proposed method is also applicable to continuous beam. Besides，appropriate vehicle-bridge mass ratio and first order vehicle-bridge frequency ratio could optimize damage identification performance.