With　the　high　speed　camera,　the　characteristics　of　thin　wire　MAG　welding　process　with　high　current　density　including　arc　shape　and　droplet　transfer　are　researched.　Through　analyzing　the　force　of　liquid　metal　cone　and　arc,　the　motion　model　of　liquid　metal　cone　is　given.　Also　the　spatial　position　relationship　and　the　motion　correlation　of　liquid　metal　cone　and　arc　are　pointed　out.　The　result　shows　that　the　motion　style　of　the　liquid　metal　cone　belongs　to　self-magnetic　rotating　which　means　the　liquid　metal　cone　deviates　from　the　wire　axis　by　a　certain　angle　and　makes　high　speed　rotation　around　the　wire　axis　under　the　actions　of　electrode　magnetic　force　and　arc　force.　The　relative　size　of　deflection　angle　of　liquid　metal　cone　is　determined　by　the　area　of　liquid　metal　cone　enclosed　by　the　arc　shining　zone.　When　this　area　increases,　the　deflection　angle　becomes　smaller　and　the　stability　of　welding　process　is　enhanced.　The　driving　force　of　high　speed　rotation　of　arc　is　supplied　by　the　magnetic　filed　of　liquid　metal　cone,　and　the　arc　deflection　angle　and　arc　rotating　angular　velocity　are　closely　related　to　the　deflection　angle　and　rotating　angular　velocity　of　liquid　metal　cone　respectively.　©　2010　Journal　of　Mechanical　Engineering.