Abstract: Fatigue tests at three stress levels were conducted on 7050 aluminum alloy lug samples with different sizes. The fatigue stress-life (S-N) curves of the lugs were obtained by the least square method. The effects of ratio of ear hole diameter to lug width d/W (d had a fixed value, 24 mm; d/W=0.67, 0.50, 0.40) and ratio of longitudinal margin to transverse margin of ear hole y/x (y/x=1.0, 1.6) on fatigue properties and fracture morphology of the lugs were studied. The results show that under the same stress, the fatigue life of 7050 aluminum alloy lugs increased first and then decreased with the decrease of d/W (namely increasing W). The larger of the y/x value, the longer of the fatigue life of the lugs. The fatigue fracture of the lugs with different sizes all had typical fatigue fracture characteristics. The cracks initiated on surfaces and at corners.