Abstract: The curves of S-N and strain-life (Ae-Nf) of HG50 steelwelded joint were investigated.The fatigue life mainly depends on elasticity strain ABe in Nf>105 times and belongs to high-cycle fatigue life that the elastic destruction is primary.The fatigue characteristic is different with the different cycle stress-life rate in low-cycle and high-cycle.The basic data are offered for fatigue-resistant design of welded structures.