In order to discuss the rationality of fatigue analysis models of bogie welded frame,this paper regards box girder as the research object and establishes nominal stress model,structure stress model and notch stress model by aiming at different processing methods of main weld. Through stress characteristics,fatigue assessment,cumulative damage,and weld parameter influence of three models are compared. The results show that stress size and orientation under nominal stress model and structure stress model have higher similarity,it is reasonable to ignore the weld for nominal stress model on condition that stress value must locate in the weld toe front,where sets the strain gauges. Characteristics of notch stress model lie in describing local stress state and cycling performance of weld really,and its advantages are also reflected in conducting fatigue assessment on both weld toe and weld root simultaneously,for the reason that fatigue failure of box girder may occur in weld root,as shown in the computed results. Because structure stress model is not sensitive to changes of weld parameters,optimization of weld parameters only chooses notch stress model.