<p>Shot peening is known process for metal strengthening in aviation manufacturing, but the single shot peening process is increasingly unable to meet the strengthening demands, and the combination of two processes for shot peening has become a research hotspot. In this paper, The effects of laser shot peening (LSP), mechanical shot peening (MSP), and combined shot peening (CSP) that combines the advantages of LSP and MSP on the aluminum 6061-T6 alloy microstructure evolution and fatigue behaviour were investigated. The study results show that greater hardness, greater residual compressive stress, thicker residual compressive stress layer and higher density dislocations were formed in the surface layer of the samples by CSP. Compared with no-shot peening (NSP) samples, the cycle life of LSP, MSP and CSP samples increased by 40.1%, 106.6% and 190.2%, respectively, and the fatigue resistance of CSP sample is better. The higher numerical residual compressive stress, thicker residual compressive stress layer and higher dislocation density formed during CSP process are helpful to improve the fatigue resistance of samples. This study will provide insights and guidance for the application of CSP.</p> Graphical Abstract <p></p>