Abstract: A double-wire pulsed MIG welding system with single power has been established,in which two wires were parallelly connected with the power source and placed on the workpiece.The current signals and voltage signals of the two arcs were collected.Synchronously high-speed photography was used to observe the metal transfer process and arc behavior.On the basis of maintaining a stable welding process,two factors,i.e., wire-wire distance in the vertical direction of the weld and arc voltage were studied.The influences on alternate arcing of the double-wire pulsed MIG welding system were analyzed.It was found that,the longer the wire-wire distance and the higher the arc voltage,the less the alternation frequency and the more obviobvious the alternate arcing.The behavior of charge particles produced in the welding has an important influence on alternate arcing.