On　the　basis　of　designing　a　longitudinal　magnetic　field　generator　with　powerful　engineering　practicability　and　miniaturized　structure,　the　longitudinal　magnetic　field　is　applied　to　streaming　transfer　MAG　with　the　shielded　gas　of　98%Ar　and　2%　O2.　Magnetically　induced　rotating　MAG　welding　process　is　put　forward.　At　the　meantime,　the　influence　on　arc　shape　and　moving　behavior,　wire　melting　character,　drop　transfer　mechanics,　and　weld　formation　of　exciting　current　is　studied.　The　shortage　of　deflecting　weld　for　this　new　welding　process　is　pointed　out.　The　result　shows　that　under　the　effect　of　the　outer　longitudinal　magnetic　field,　all　of　arc　and　molten　cone　and　liquid　metal　jet　deflect　from　the　wire　axis　and　rotate　with　high　speed.　The　larger　of　the　exciting　current,　the　faster　of　arc　rotating　angular　velocity,　the　shorter　of　arc　length,　the　faster　of　drop　transfer　frequency,　the　lower　of　welding　current　and　the　larger　of　wire　melting　coefficient.