The use of the Friction Stir Welding (FSW) process in aircraft construction, naval or nuclear reduces manufacturing costs and indirectly, operating costs through structural lightening. The aluminum alloys have very interesting specific properties such as very good electrical and thermal conductivity, good ductility accompanied by good mechanical and corrosion resistance. It is for this reason that these alloys are used in many industrial sectors. The aluminum based alloys are difficult to melt weld due to their high thermal conductivity and oxidation rate at temperatures very close to that of melting. The purpose of this investigation is to study the variation of the surface roughness on the weld joint of 5 mm thick plates of AA6061-T6 using friction stir welding FSW and carried out using a simple form pin tool.  Surface roughness of FSW joints as a function of welding parameters (rotational speed, welding speed). The surface roughness of FSW joints has a big impact on the fatigue of the welded joint, hence determining the minimum surface roughness is critical. The quality of an FSW joint is heavily influenced by the tool and welding settings. The tool's geometry affects both the heat distribution and the amount of metal entrained by the tool. This paper provides outcome of impact of welding parameters on microhardness, and surface roughness of friction stir welded AA6061- T6. Conclusions derived from this research work are: the FSW joint's microstructural examination reveals homogeneous particle distribution.