Research conclusions:(1)The stress calculated by computer space rigid model can be directly used to fatigue design， and need not to be corrected by structural factor. The problem faced by designer can be solved，which is that the results calculated by computer space rigid model cannot be used to fatigue design. (2) Through a lot of research，measurement and calculation，the typical operation train and fatigue load spectrum under the current transport situation are determined. It makes the fatigue design closely follow up the current transport situation.(3)Fatigue design partial coefficients are studied，and the fatigue limit state design methods of intercity railway，high speed railway and freight railway are established. It fills the blank of fatigue design in intercity railway, high speed railway and freight railway. (4) The typical steel bridge has been designed according to the fatigue design method based on the new situation，the design results show that the reserves of the fatigue design methods under the new situation compared with the existing fatigue allowable stress design method is increased slightly. Research results will be incorporated into “railway bridge design specifications(limit state design)”，and will be directly used to design the new steel bridges in future，and can provide a reference for fatigue assessment of existing railway steel bridge.