Medium and small span bridges make up a large proportion of highway bridges in China. Due to harsh service condi? tions， the expansion joints are prone to diseases， which can exacerbate vehicle vibrations， and subsequently lead to the damage of the end bearings and other components. In order to study the influence of expansion joint and bearing parameters on the vehicle-in? duced dynamic response of simply supported beam bridge， this paper establishes a numerical analysis method of vehicle-expansion joint-bridge coupling dynamic response （VBCV-J）. The effectiveness of VBCV-J analysis method is verified using measured data， followed by an investigation the influence of expansion joint and support parameters. The results show that： The speed is closely re? lated to vehicle vibration. When the vehicle speed is high and the Road Surface Condition （RSC） is “normal”， the impact effect of vehicles on expansion joints and the ends of beams can exceed the specified values.. If the girder in the expansion joint is higher than the pavement， the impact on the expansion joint will significantly increase， conversely， it will decrease. When the girder in the ex? pansion joint is higher or lower than the road surface， the impact at the end of the main beam will increase. A reduction in the sup? port stiffness of the expansion joint or a void in the side support of the main beam will significantly increase the impact effect on both the expansion joint and the end of the main beam. A decrease in the stiffness of the main beam support primarily results in an increased impact on the entire main beam. Damage to the expansion joints not only affects their own impact， but also greatly in? creases the impact on the end members of the simply supported beams. During design and maintenance， sufficient attention should be given to the end members of the beams.