Energy　dispersion　and　easy　instability　associated　with　arcs,　the　traditional　metal　processing　heat　source,　restrict　its　development　and　application　in　the　modern　high-precision　welding　and　additive　manufacturing.　This　work　aims　to　study　the　characteristics　of　a　novel　arc　under　circumferential　gas　constraint　effect　which　can　improve　the　arc　stability　and　processing　accuracy.　A　magnetohydrodynamics　model　was　established　to　calculate　the　arc　physics　and　heat　transfer,　considering　the　electron　emission　characteristics　of　tungsten　and　the　effect　of　metal　vapor.　It　indicates　that　the　annular　flexible　constrained　gas　flow　can　significantly　increase　the　physical　characteristics　such　as　arc　temperature,　plasma　flow　velocity　and　current　density　compared　with　traditional　free　arc　which　is　named　GTA.　The　arc　heat　generation　increasement　of　the　novel　arc　makes　the　heat　transfer　from　arc　to　base　metal　higher　than　that　of　GTA.　The　additional　annular　gas　flow　inhibits　the　diffusion　of　metal　vapor,　stabilizing　the　arc　and　protecting　the　tungsten　electrode　from　contamination.　However,　as　the　arc　length　decreases,　eddy　of　arc　plasma　flow　appears　inside　the　arc,　which　can　cause　metal　vapor　to　contaminate　the　tungsten.　It＇s　found　that　this　novel　gas　flow　constrained　arc　needs　to　be　applied　with　a　small　current　when　welding　with　small　arc　length　to　avoid　the　eddy.　Finally,　the　accuracy　of　the　calculation　model　is　verified　by　experimental　detection　of　arc　temperature.