Abstract: 6061-T6 aluminum alloys were butt welded by stationary shoulder friction stir welding with different welding parameters of heel plunge depth,rotation speed and welding speed. Influence of welding parameters on microstructure and mechanical properties of joints was investigated. The results showed that the weld surface was smooth without upset metal under all parameters. Welding parameters could affect the liquidity of material,and then influenced on joint formation,microstructure and mechanical properties. Welding parameters could significantly affect the shape of nugget zone,when the shape was spherical,microhardness of the weld could be symmetrical distribution like W. However,when the shape was bowl-shape,microhardness of advancing side was slightly higher than that of retreating side. Under optimal parameters,namely,heel plunge depth of 0. 08 mm,rotation speed of 1 600 r/min and welding speed of 500 mm/min,maximum tensile strength of the joint was 224 MPa,reaching 75. 6% of that of the base material.