Abstract: In order to obtain a realistic heavy traffic load diagram of long-span steel bridge, a three-dimensional finite element model of heavy radial tire 10.00 R20 was established. The grounding shape, grounding area and pressure distribution of simulated tire under different axle loads on steel bridge surface under three load positions were analyzed. The results showed that the simulated tire inflation deformation, the ground area and pressure acting on the road surface were close to the measured results, which verified the reliability of the composite tire model established by the finite element method. The ground area of heavy-duty tire acting on steel bridge deck was similar to that of road surface, but the average ground pressure was higher, and the non-uniformity of pressure distribution can’t be ignored. Finally, the diagram of double-wheel rectangular uniform traffic load on steel deck was proposed and the non-uniform coefficient was given to characterize the most unfavorable response.