Abstract: 7A52 aluminum alloy was welded by using 5A56 filler with twin wire gas shielded arc welding.The mechanical properties and microstructure of welded joint were studied.The results show that the weldability of 7A52 aluminum alloy is good.The weld zone is the weakest in welded joint due to effects of chemical components of filler and crystallization process.Therefore twin wire gas shielded arc welding of medium and thick 7A52 aluminum plate can obtain excellent welded joint.