Friction stir welding (FSW) broadly used in the same grade as aluminium alloy but for aluminium alloy material it requires high speed rotation of FSW tool which develops high temperature on tool. In this paper process parameter of FSW are studied based on the strength of welding joint and predict FSW tool speed as low as possible according to the past literature. Constant machining parameters are tool rotation of FSW is 800 rpm and welding speed 15 mm/min. In this work analysing the strength variation of welding joint under two mode of pre-heating temperature on the work-piece then variation of cooling medium apply after preheating to change the grain structure of work-piece. In this work the FSW process is passed over two pieces of aluminum at once and the effect of tool rotation and temperature of the tool is discussed by preparing the sample for testing according to the ASTM dimension.