In this paper, the features of weld formation, porosity, arc behavior, microstructure and mechanical properties of 6061 Al alloy thin sheet welds by direct current (DC) double pulse metal inert gas (MIG) welding process are investigated and compared with the traditional DC MIG welding process. Results show that continuous one-side welding with back forming weld beads without spatters, undercuts or cracks can be obtained by using the DC double pulse MIG welding process. The porosity of weld bead can be largely reduced by using the process. The arc of DC double pulse MIG welding is stable without arc blowout, and the metal transfer model of DC double pulse MIG welding is better than that of DC MIG welding. Microstructure of the weld bead by DC double pulse MIG welding shows a dendrite structure and it is fine and uniform. The average ultimate tensile strength and elongation of the weld bead by DC double pulse MIG welding can get to 228MPa, 80% of base metal, and 7.6%, 63% of base metal.