Abstract: With the help of a high-speed camera, the image signals of the four-tungsten-electrode TIG arc during the ignition discharge process and stable combustion process were collected, and the characteristic parameters of the arc were quantitatively changed. The influence of the tungsten electrode spacing, arc length, and deposition current on the coupling process and stability of the four-tungsten-electrode TIG arc were analyzed, thus obtaining the stable combustion mechanism of the four-tungsten-electrode TIG arc and the key factors affecting the multi-arc thermal effect. The results show that for a certain range, the stability of the single-tungsten-electrode arc is better with the deposition current of ≤ 160 A, the arc length of ≤ 5 mm, and the tungsten electrode spacing of ≤ 6 mm. Compared with that of tungsten electrode spacing, the influence of arc length and deposition current on the shape of the arc is relatively small. Tungsten electrode spacing can significantly affect the stability of the four-tungsten-electrode TIG arc. When the tungsten electrode spacing is 2 mm, the four-tungsten-electrode TIG arc attracts each other under the action of self-magnetic contraction and Ampere’s force; the four-tungsten-electrode TIG arc forms a common conductive channel. In this case, the stability of the four-tungsten-electrode TIG arc is the best, and the effective utilization rate of the heat source is the highest. When the tungsten electrode spacing is 8 and 10 mm, both the arc stability and the effective utilization rate of the heat source are significantly reduced. When the tungsten electrode spacing is 2 mm, the melting energy is approximately 9.2 times that when the tungsten electrode spacing is 10 mm.