Abstract: The twin arc pulsed GMAW(gas metam arc welding) process possesses the advantages of high efficiency and automation, and is a process with great application foreground.The matching ways between the external characteristics of the pulse output stage and that of the pilot arc stage can take great influences on the welding arc stability, metal transfer and the appearance of weld, etc.A novel twin arc soft-switching pulsed GMAW system was developed and used to explore the three kinds of typical hybrid external characteristics in depth from the aspects of arc length control, metal transfer and appearance of weld.The experimental results indicate that the master power I-I, slave power I-I hybrid external characteristic is with good controllability of the metal transfer and suitable for the high speed welding of the thin plate, except for the poor adaptability of the welding arc length;the master U-I, slave U-I hybrid external characteristic is with good adaptability of the welding arc length control and is suitable for the welding of the slab work piece, except for the poor controllability of the metal transfer;in the master I-I, slave U-I hybrid external characteristic, the master arc is with good controllability of the metal transfer and limited selfadaptability of the arc length, and the slave one is with good selfadaptability of the arc length and poor controllability of the metal transition.