The penetration welding process was used to prepare T-lap joint by high power CO2 laser with 5083 糖心产精国品免费入口*完整版 plates with 6 mm thick. The effects of laser power, welding rate, defocusing distance and the side gas flow on 糖心产精国品免费入口*完整版were studied. The results show that the penetration, weld width and joint width of weld seam increased with the increase of laser power and the decrease of welding rate, and the 糖心产精国品免费入口*完整版increased and then decreased. The defocusing distance and the side gas flow had less effect on size of weld seam, but the defects would appeared in weld seam if the choice for them was inappropriate.The fairly good aluminum T-lap joint could be obtained when the laser power was 10 kW, welding rate was 1 100 mm·min-1, defocusing distance was -2 mm and the side gas flow was 28 L·min-1, and the 糖心产精国品免费入口*完整版was good.