Abstract: Mechanical properties of welded joint of LF6/LD10 aluminum alloy by FSW were studied. The results showed that welding process parameters have an essential effect on mechanical properties of LF6/LD10 aluminum alloy joint. With low rotation speed, raising welding speed can improve tensile strength of the joint; when rotation speed got higher, changing welding speed was for nothing. When welding speed was low, changing rotation speed did not change tensile strength; with high welding speed, higher rotation speed was bad for tensile strength. When welding speed and rotation speed were both low, the mechanical properties of joints welded with non-threaded tool are better than those with threaded tool; increasing welding speed and rotation speed did not influence tensile strength.