Abstract: In this paper, the effect of structural details on fatigue crack initiation and propagation in butt welds of 16Mn steel is investigated and a procedure to predict fatigue life of the butt welds is outlined. The results indicate that the specimens butt-welded by two piece of steel plates with different width or different thickness have almost the same fatigue life as those welded by two piece of the steel plates with equal width and equal thickness, if the weld reinforcement is not machined off. The fatigue resistance of the butt welds can be improved by means of removing the weld reinforcement and designing the weld in the maximum shear stress plane. When there exists no crack-like defect, the fatigue life of the butt wcJds is the sum of crack initiation life and crack propagation life, which should be predicted respectively.