Abstract This study presents a modified triple-wire indirect arc welding method to improve melting efficiency of the base metal. To achieve this, a mirror-symmetrical wire arrangement was adopted because of small arc distribution space and the electrode polarity is changed different from the previous triple-wire indirect arc welding method. The arc shape is observed with the novel wire arrangement, and the bead-on-plate welding experiments arecarried out and the melting efficiency of the base metal was calculated. Results reveal that the adopting welding wire polarity of the main wire and the side wire respectively acting as anode and cathode can superimpose the two indirect arcs into a single indirect arc which increases the arc energy concentration. The main reason is that the indirect arcs deflect to the main wire and the arc voltage is improved. As a result, the penetration, the melting area and the melting efficiency of the base metal are improved to varying degrees with increasing current. For instance, at the current is 400A, they were increased to 2 times, 3 times and 2.55 times, respectively. Meanwhile, a single pass butt joint of 10mm plates by the modified triple-wire indirect arc welding with low energy consumption and high efficiency is successfully accomplished.