Abstract: Triple-wire gas indirect arc welding is a new and efficient welding method. In order to study the effect of wire extension on TW-GIA welding, welding analyzer and high-speed imaging equipment were used to collect the arc, droplet, current and voltage in the welding process.The results show that it is difficult to form a stable welding process when the extension of the main wire and the side wire is not equal. When the extension of main wire and side wire was equal, with the increase of wire extension, the concentration of arc became worse, the fluctuation of current and voltage increased, the droplet size increased, and the angle between main wire droplets and side wire droplets increased. When the extension of main wire and side wire was 10 mm, the welding process was the most stable and the bead formation was the best.