Abstract: In order to recognize the importance of the addition of trace nitrogen in the triple gas mixture, the difference of the aluminum welding was studied in terms the arc shape, macro and micro-welded joint structure, the width of heat affected zone, by using pure argon, binary Ar-He mixture, triple Ar-HeN₂. In comparison to the MIG welding using pure argon and ArHe, the arc was more concentrated that allow a production of best quality of joint with highest impact toughness and narrow HAZ.The performance of the welding joint using pure argon was the next-best. The work shows that adding trace nitrogen is a very important factor for the improvement of welding quality using ArHe-N₂ triple gas shielding.