The influence of different phase matching between lead and trail machines on the arc of tandem twin wire pulsed gas shielded welding is studied. There are four stages in the phase matching of lead-trail machine twin wire coordinated welding. Mode 1 is that the lead and trail machines output pulses at the same time,at this time,the lead-trail machine pulse is in phase matching;mode 2 is that the lead machine arrives at the pulse peak stage,and the trail machine starts to output pulse;mode 3 is that the lead machine is at the pulse descending stage,and the trail machine outputs pulse;mode 4 is that the lead machine is at the basic value stage,and trial machine starts to output pulse. The second generation twin wire welding system newly developed by Panasonic is used to carry out welding test. The results show that in mode 1,because the two arc of lead-trail machines are in peak stage at the same time and completely coincide,the interference is large,resulting in large spatter. In mode 2,the peak phase of the lead-trail machines overlaps,and there is arc interference,which is smaller than that in mode 1,and there is also large spatter;In mode 3,the lead machine pulse droplet begins to fall off. If the trail machine starts to output pulse at the early stage of the lead machine pulse falling edge,it will produce arc impact on the metal transfer of the lead machine and generate spatter,which is smaller than that in mode 1 and mode 2. When the falling edge of the lead machine is close to the basic value,the trail machine outputs pulse again,the spatter is small and the arc is stable. In mode 4,the lead machine enters into the basic value stage and is in the arc maintenance period,and the current is small. At this time,the trail machine outputs pulses,and the arc of lead machine may be broken. If the arc of lead machine is normal,the welding effect is good,the spatter is small and the shape is beautiful. When the lead machine is at declining stage and droplets fall off,the trail machine outputs pulse,and the phase matching is the most appropriate and the welding effect is the best. When the set voltage or extension length of welding wire of the lead machine changes,the phase matching time is automatically adjusted.