Abstract: To reveal the mechanism of interference and arc interruption during triplewire GMAW, signal acquisition system and highspeed camera synchronous acquisition system were developed, which sampl the welding electric waveform and arc features of triplewire GMAW. The factors of arc deflection were analyzed based on electromagnetic theory and it is concluded that arc interruption frequency decreases with the increase of interwire distance, welding current increase and with decrease of welding current. The experimental results show that there is no arc interruption of triplewire GMAW by properly selection of interwire distance and welding current combination on a base of theoretical analysis. And the longer arc length brings about arc plasma upward and arc interruption occurs due to electromagnetic force among arcs.