Friction stir welding (FSW) is a solution to overcome the problems of AA 6061 welding. When the initial temperature T0 of the material is increased during the FSW process while the FSW process parameters are kept constant then FSW welding parameter value can be lowered. T0 was varied by Troom temperature, 50 0C, 75 0C, 100 0C and 125 0C. The weld joint design form is a square butt joint. By using this approach the higher the T0, with the FSW parameter being kept constant, produce the higher the welding peak temperature and cooling rate, the smaller and smoother the metal grain structure in the weld nugget, TMAZ and HAZ, the higher the hardness of the weld nugget and the higher the tensile strength eventough welding defects in the form tunneling, kiss bond, and void are still observed.