In order to explore the application of hammer system in bridge dynamic test, standard span simply supported T-girder bridge, box girder bridge and hollow slab bridge were selected as the research objects, and the research on deflection dynamic load allowance (DLA) test of simply supported girder bridge were undertaken, adopting numerical simulation and experimental verification. The vehicle-bridge-hammer coupling vibration analysis program was compiled based on ANSYS software, combining with numerical calculation and response surface analysis, deflection DLA test results of suspension hammer method and scaffolding method were compared to explore influence of suspension length, wire tensile stiffness and suspension hammer mass on the accuracy of the DLA tested by suspension hammer method. Furthermore, the suggested value of suspension hammer system parameters was proposed. Finally, a 30m simply supported box girder bridge was tested under dynamic load. Dynamic deflection of the bridge was tested by scaffolding method and suspension hammer method to verify the proposed parameter suggested value. Results show that in order to meet requirement, difference between deflection DLA measured by suspension hammer method and scaffolding method is less than 5%, the optimal values of wire tensile stiffness and suspension hammer mass increase with wire length. The research results can provide theoretical basis for DLA test of bridge load test.