Abstract: In this paper,the problems of arc wandering and instability have been studied with extra transversal magnetic field for low current TIG welding.The influence of extra magnetic field frequency(0~10kHz) on the arc appearance has been observed.The arc swing is in synchronism with magnetic field in low frequency,so the arc appearance is expanded.The arc is calmed in medium frequency,and is compressed in high frequency,thus increasing the arc energy density,the arc stiffness and the arc voltage.When other conditions remain unchanged,with increased intensity of magnetic field the said phenomena are intensified accordingly.Experiment results of welding thin sheet indicate that by using magnetic field to control the arc,the wandering of arc can be restrained and the arc stability and shape improved markedly.