Abstract: Single supply AC twin-electrode GTAW experiments of 6061 aluminum alloy were carried out. The microstructures of aluminum alloy joint were analyzed by optical microscopy, while the arc static characteristics and current change in welding process were investigated by CCD camera and current detection system. The results showed that acceptable joints without obvious defects are obtained with double tungsten electrodes under high current condition, but the tandem tungsten electrodes are better than parallel arranging of in welding process. The current detection results showed that the total current is assigned randomly by two GTAW torchs, and current density of single tungsten electrode presents unimodal distribution along welding direction, while double tungsten electrodes has the current density with double peak. In arc region, current density of coupling arc is less than that of single arc. Double tungsten electrodes not only expand the root of the coupling arc, but also increase the heating area of molten pool.