A　three-dimensional　transient　turbulent　model　of　plasma　arc　was　established　based　on　local　thermodynamic　equilibrium　(LTE)　to　study　the　effects　of　arc　current,　argon　flow　rate　and　hydrogen　flow　rate　on　arc　fluctuation　inside　the　argon-hydrogen　plasma　torch　by　using　computational　fluid　dynamics　software　ANSYS　CFX.　The　results　show　that　when　the　arc　current　increased　but　less　than　600　A,　the　arc　column　became　shorter,　the　average　arc　voltage　and　the　arc　fluctuation　decreased,　but　the　fluctuation　frequency　increased.　However,　when　the　arc　current　increased　to　above　600　A,　it　had　little　influence　on　the　arc　fluctuation.　The　increase　of　argon　flow　rate　or　hydrogen　flow　rate　led　to　the　increase　of　the　arc　column,　average　arc　voltage　and　voltage　fluctuation,　but　decrease　of　the　fluctuation　frequency.　Among　three　process　parameters,　hydrogen　flow　rate　affected　the　arc　fluctuation　most,　and　the　arc　current　did　least.