The ultrasonic peening technique (UP) is one of the innovative and hopeful methods for fatigue life enhancement and upgrading of welded structures and components. The fatigue testing of sheet specimens for 6061-T6 aluminum alloy, demonstrated that the UP is an effective change treatment to mechanical properties as judged against unpeened specimens. S-N curve and the fatigue fracture mechanism were scrutinized in detail. The most important results revealed the fatigue life of specimens improved due to the surface hardening. Residual compressive stresses were created by UP and increased the fatigue life and strength. This paper scrutinized the potential use of ultrasonic waves on the surface of 6061-T6 aluminum alloy. This can be exhibited as a factor of safety due to ultrasonic, reach to 1.42 when estimate the number of cycles fatigue based on amount of applied stress at 0.3 u.