Different ideas exist on arc stability mechanism of laser-arc hybrid welding process. With high-speed camera and spectrometer, contrast analysis and research are made between method active gas (MAG) arc welding and hybrid arc welding in this paper. The results show that hybrid arc takes on a new shape and has two electric conduction paths independently. This phenomenon is called "double electric conduction mechanism" of the laser-pulse MAG hybrid welding process. This mechanism plays a very important role in maintaining arc stability and getting good appearance of weld during high speed welding process. It is also shown that the establishment of double electric conduction channel exists time sequence. The additional electric conduction channel ignites originally from the laser keyhole and then extends gradually to the whole space of the arc. Welding parameters, including distance between laser and wire, arc voltage and welding speed, have obvious influence on the double electric conduction mechanism.