Abstract: 2 mm thick 6061-T651 aluminum alloy welded by laser welding with filler wire was studied.The microstructures of weld seam,morphology and compositions of precipitated phases were analyzed by optical microscope,SEM and XRD,respectively.Moreover,the microhardness of the welded joint was tested by using microhardness tester.The analyses results show that the size of grains in weld seam is small while the heat affected zone is narrow.In addition,strip shaped and granular precipitates,whose existence has a significant influence on the weld mechanical properties,are evenly distributed in the weld seam.The hardness of weld seam is much higher than those of the heat affected zone and the base metal,which is related to the large number of enhanced phase exists in the weld seam.