Modification of conventional gas metal arc welding (GMAW) process is of great potential to achieve high productivity with low cost and strong usability.Double-Electrode GMAW (DE-GMAW) is such a modified arc welding process which is formed by adding a bypass torch (gas tungsten arc welding torch) to a conventional GMAW system.The mechanism of metal transfer in DE-GMAW was proposed and verified in this paper.Experiments show that the critical current is decreased so that spray transfer can be obtained at a lower current level in DE-GMAW.Analysis of this significant change in metal transfer phenomena is conducted, and explanation is given out.It is found that the bypass arc in DE-GMAW lifts the anode point on the droplets such that the electromagnetic force becomes larger and squeezes the droplets so that spray transfer can take place under welding current lower than that in conventional GMAW.