Al-alloy is utilized widely as a light-weight material to an automobile, a vessel and many kind of equipment, due to the light-weight and its characteristics that is a good tensile strength, elongation and tenacity for bearing heavy load and weight. Al-alloy has the good property of hot working, cold working and corrosion-resistant. But the exiting fusion welding by using Al has some economical and technical problems, but on the other hand, Friction Stir Welding (FSW) that is new joining method can settle the disadvantages that occur to the fusion welding and Is being applied and extended into the various industry fields. On this study, To analyze accurately the mechanical properties of joining area by FSW in Al 6061 alloy by using finite analysis program with finite element method. The size of HAZ and the thermal distribution is simulated and the mechanical properties around the FSW joining area to the Al-alloy 6061 is examined.