Taking a three-span continuous box girder bridge as the research object, a bridge model and a vehicle model are established to form a vehicle-bridge coupled dynamic model, and the impact coefficient of the bridge structure under the action of vehicle load is studied and analysed. The study shows that: the number of transverse lanes increases the impact coefficient of the bridge, the greater the longitudinal distance the smaller the impact coefficient of the bridge; the impact coefficient of the bridge in the braking state of the vehicle is significantly greater than the impact coefficient of the vehicle at constant speed, and when the vehicle brakes in the first half of the bridge mid-span, the power impact coe-fficient is greater than the second half of the span; the vehicle in the jump impact effect, the impact coefficient of the bridge mid-span increases significantly, and in the mid-span jump when the vehicle The bridge power impact coefficient is the largest.