In the present work, laser shock processing (LSP) using a Q-switch YAG laser facility with high pulsed peak power under water environment is implemented near the toes of A6061-T6 Aluminum alloy metal-inert gas (MIG) welded joints. And the properties of A6061-T6 aluminum alloy MIG welded joints is analyzed before and after laser shock processing through the comparative method. The results show that after laser shock processing, Vickers hardness and fatigue life of the welded joints have been significantly improved, fatigue fracture of the welded joint without laser shock processing is located in or near the welded while it is located on the base material after laser shock processing, and a larger near-surface residual compressive stress with a maximum value of about -145 MPa is obtained. Compared with the base material, the surface roughness deteriorates after laser shock processing.