The surface of 6061-T6 aluminum alloy welding line and heat-affected zone by tungsten inert gas (TIG) is processed by high power and high repetition-rate Nd∶YAG laser. The contrast test is completed through adjusting the parameters of laser energy and laser shock processing (LSP) path. The safety lives of welded joint specimens with and without LSP are estimated by making low cycle tensile fatigue test. The effect of LSP on fatigue properties of aluminum alloy welded joint is analyzed. The fatigue fracture mechanisms of these specimens with and without LSP are studied by fracture surface, scanning electron microscope (SEM) energy dispersive spectrometer (EDS), residual stress and hardness analysis. The result show that the safety life of 6061-T6 aluminum alloy welded joints is increased 117.1%. The welded joint specimen which has the longest fatigue life is processed by LSP with laser energy 5 J, shock area 18 mm×16 mm and double shock. Compressive residual stress is induced at the surface of welded joints by LSP. The hardness of welded joints are significantly improved after LSP.