Abstract: The fatigue behavior of friction stir welded (FSW) joint and metal inert-gas welded (MIG) joint of 6082-T6 aluminum alloys of 10 mm in thickness were studied by fatigue test. The microstructure of joints and fatigue crack propagation were investigated by optical microscopy and scanning electron microscopy. The results demonstrated that under cycle times of 2×10⁶, the fatigue strength of base metal (BM), FSW joint and MIG joint are 126.3, 110.2 and 84.2 MPa, respectively. Moreover, under high stress level (σ=160 MPa), FSW joint fatigue life is significantly greater than that of MIG welded joints, and equivalent of that of the base metal. MIG joint fatigue fracture occurs at the weld toe, and the porosity defects is the main crack initiation. Most of FSW fatigue fracture appears on the shoulder edges. The micro-fracture appearance has the characteristic of quasi-cleavage pattern, and fatigue striation and dimple appear on fatigue fracture appearance.