Abstract: Experiment of flat butt-welding is conducted on the Al-13.0Si-0.7Mg alloy on T6 state with two kinds of welding wire, ER4047 and ER5183. The process of double pulse MIG welding by both sides is used to reduce the influence of welding heat input on the base metal. The welding parameters of two welding wires are confirmed and the good weld formations are obtained. The alloy and the two wires to this alloy have good heat cracking resistance as fish-bone cracking test shows. On this basis, the microstructure observation and mechanics performance testing are conducted on the welding joints. The results show that the microstructure of joints is different for these two wires. The tensile strength of the welded joints is about 70% of the one of base metal. The hardness test indicates that there is softening phenomenon in the heat-affected zone.