Abstract: In this paper, the microstructure, microhardness, residual stress and fatigue test of ultrasonic impact before and after the processing of 7A52 aluminum alloy welded joint were analyzed. The results showed that joint plastic deformation layer thickness was about 45 to 70 μm, base metal hardness increased by 170%, weld surface hardness increased by 70%, after ultrasonic impact treatment. In fatigue tests, when the cycles were 2×10⁶ times, the loading stress cycle ratio was 0.1, the fatigue strength of the impact of state joint was 60.26 MPa, increased by 47.9% than the welded specimen fatigue strength was 40.74%. In the loading cycle stress ratio was 0.45, the fatigue strength of the impact of state joint was 46.53 MPa, increased by 16.4% than the welded specimen fatigue strength is 39.97 MPa.