Abstract: Self-developed TJU-HJ-I ultrasonic fatigue test device and conventional fatigue test device were used to test the fatigue performance of 5A06 aluminum alloy TIG welded joints. The ultrasonic fatigue fracture morphology of specimen was observed by scanning electron microscope. The results revealed that 5A06 aluminum alloy flush welded joint did not show an influence of cyclic frequency on lifetimes in the high cycle fatigue regime. And ultrasonic fatigue test results can be used to characterize the safety of long-term used mechanical structure. It was proved that if the location of the pore was with small depth from the surface, a small value of fatigue cycles would be got without considering the size of the pore. The inclusions in the weld introduced during the welding process were oxide. The oxide had large density and had effect on fatigue properties.