Abstract: The overall bridge FE model and simplified steel bridge deck FE model were built． The boundary conditions of diaphragm fatigue detail FEM were interpolated from the FEM of the steel bridge deck． The local stresses under variable wheels lateral distribution were calculated． Influence of diaphragms parameters on fatigue damage of diaphragm fatigue detail was investigated． The results showed that the differences of stress amplitude between the FEM of mixed-element and simplified steel bridge deck were less than 5. 0%． It was simple and reliable to calculate the fatigue stress of diaphragm fatigue detail by using steel bridge deck model． Stress amplitude of diaphragm fatigue detail reached maximum when the off-center distance of wheel position was 150 mm，which decreased obviously with the increasing off-center distance of wheel position． Stress amplitude of diaphragm fatigue detail increased with the increasing interval of diaphragms． And increasing diaphragms thickness could improve the fatigue behavior of stress of steel bridge deck．