Abstract: The structural stress of 7N01 non-load bearing cruciform joints with different geometrical magnitude under fatigue loading was calculated, and the corresponding master S-N curve was obtained. The results show that, compared with the nominal stress based S-N curve, master S-N curve based on structural stress method shows much better linear correlation for cruciform joints with different geometry. The influence of plate thickness on fatigue strength was then analyzed. The results show that the relationship between load bearing ability and plate thickness is nonlinear. When nominal stress remains the same, fatigue life is reduced when plate thickness is increased.