Abstract: The multi-electrode arc test system was established with the data acquired by card and high speed camera. Its function was acquired by the welding arc electronic signals and high-speed image synchronously. With this system,an analysis of the behavior of the multi-electrode arc was conducted.The changes in the arc behavior were due to the change of electric field strength which was in the cathode polar region( polarity effect). The experiment results show that the polarity effect can reduce the stability of the DE-GMAW and promote the stability of the arcing-wire GTAW. The fact that the behavior of the cross arc changes is beneficial to metal transfer.