The purpose of this work was to investigate the effect of activating fluxes and welding parameter to the penetration and depth-to-width ratio (DWR) of 6061 aluminum alloy welds. Bead-on-plate argon gas tungsten arc (GTA) welding process was made on 6061 aluminum alloy of plate without filling metals. The activating fluxes used in the experiment were CaO, ZnO, SiO2, TiO2, Al2O3, Cr2O3, CaF2 and Na2CO3. Based on the higher penetration of weld bead and welding arc voltage, four fluxes were selected to create three new mixtures using 50% of each original fluxes. The mixed fluxes were used to investigate the effect to the welding penetration. Finally, The Taguchi method was employed to achieve optimal DWR of weld bead and investigate the welding parameters that significantly affect welding quality. The experimental procedure of GTA welding with activating flux via the Taguchi method produced full penetration of weld bead on a 6.35 mm thickness of 6061 aluminum alloy plate with single pass weld.