Laser shock peening (LSP) is an advanced surface strain strengthening and anti-fatigue manufacturing method. In this paper, LSP was employed to treat 7050 aluminum alloy fillet structures. Residual stress distribution and high cycle fatigue performance were investigated by numerical simulation and experiment, respectively. Further, fatigue life extension was verified with mathematical statistics methods. Results show that by utilizing the following LSP parameters: pulse energy of 25 J, spot size of Φ4.5 mm, overlapping rate of 50%, and peening twice, the average compressive residual stress on the fillet structure surface reached 218.3 MPa, the maximum residual stress in the depth direction located at a depth of 0.9 mm, and the thickness of residual stress affecting layer was 1.6 mm. Besides, the high cycle fatigue life significantly improved after LSP. The average high cycle fatigue life of LSPed side was 160626 cycles, compared to 58606 cycles of the BM side. Further, by using The t-test method of paired comparative experiments, we confirmed that the high cycle fatigue life of LSPed side was 2.18 to 3.36 times higher than that of the BM side at the confidence level of 95%.
