This paper studied the vehicle dynamic performance of orthotropic steel deck (OSD) bridge at fatigue details, based on a series of field tests on a 35 t 3-axle calibrated tractor across Fochen New Bridge (a three-span continuous steel box-girder OSD bridge) as well as finite element analysis. The results of the field tests were first filtered to remove the noise signal. The strain range and cycle times of each strain gauge were then obtained by using rain flow method. The impact factors of fatigue details were eventually calculated. The research shows that in both the crawl case and general speed case, the OSD bridge has obvious vehicle-bridge coupling vibration. Due to the differences in local stiffness and geometric construction at each fatigue detail, the impact factors at each fatigue detail exhibit different values. For instance, the impact factors of steel deck, U-rib, and cut-out in diaphragm are 0.219, 0.245, and 0.394, respectively, which are all larger than 0.15 specified by “Orthotropic Steel Bridge Design and Maintenance Guide” and AASHTO specification. Therefore, the current vehicle design specification underestimates the vehicle dynamic response of the OSD bridges.