Abstract: The 4mm thick 6082-T6 aluminum alloy plates were butt joining by using bobbin tool friction stir welding.The microstructure and mechanical properties of the joint were investigated. The results show that dynamic recrystallization occurs in the nugget zone (NZ), and the microstructure is typical equiaxed fine grains. Under the press amount of 0.2 mm, stirring head speed of 700 r/min, welding speed of 300 mm/min, the tensile strength of the joint is 222.4 MPa, reaching 70.1%of the base material. The joint breaks in the heat-affected zone, presenting typical ductile fracture mode. The hardness distribution of the welded joint in cross-section shows the shape of"W", and the lowest hardness position of the joint is in the heat affected zone. The positive and negative bending strengths of the joint are both about 24 MPa. Under the downward extrusion of the surface thread of the stirring needle, the weak connection phenomenon occurs under the intersection of the upper and lower plastic flow materials in the near lower shaft shoulder area, which leads to the bigger fracture degree of the back bending specimen of the joint.