Characteristics of shipbuilding T-section aluminum alloy have been analyzed. The method of laser welding shipbuilding T-section aluminum alloy has been put forward. Fillet welds of 6.0 mm thick 5083 aluminum alloy T-joints have been completed through laser beam welding with wire filler material. Based on plate welding, the influences of laser beam incident angle, working position and relationship between welding speed and wire feeding speed on shaping of welds have been studied. On the condition of 3300～3500W laser power, 0 mm defocusing length, Ar and He blending shield gas, 22°～25° laser incident angle, 0.8～1.0 mm from laser working position to the cross plate, 2.2～2.5 m/min welding speed and 2.5～2.8 m/min wire feeding speed, satisfied weld shape can be achieved. The reasons of porosities production and process instability in CO2 laser welding shipbuilding T-section aluminum alloy are also discussed.