As　the　environmental　pressure　increases,　the　arc　plasma　of　dry　hyperbaric　gas　metal　arc　welding　(DH-GMAW)　contracts.　This　phenomenon　leads　to　decreased　arc　stability　or　even　arc　extinguishment,　which　severely　affects　the　welding　quality.　In　essence,　the　dynamic　behaviour　of　arc　plasma　is　influenced　by　its　electrical　conductivity.　Furthermore,　changes　in　electrical　conductivity　depend　on　changes　in　arc　energy　transport.　To　study　changes　in　arc　energy　transport,　the　energy　dissipated　from　the　arc　to　the　external　environment　was　measured.　The　arc　voltage　drop　was　measured,　and　the　arc　conductivity　was　calculated.　A　water　heat　exchange　system　was　used　to　collect　the　energy　dissipated　from　the　arc　to　the　external　environment.　A　double　passive　tungsten　probe　was　used　to　measure　the　voltage　drop　of　the　arc　column.　Comparative　research　on　arc　energy　dissipation　and　conductivity　under　different　environmental　pressures　was　conducted　to　analyse　their　effects　on　arc　stability.　The　experimental　results　show　that　as　the　environmental　pressure　increases,　the　arc　energy　dissipation　increases,　and　the　arc　column　voltage　drop　decreases.　The　electrical　conductivity　decreases　with　increasing　environmental　pressure,　indicating　that　the　internal　energy　of　the　arc　decreases.　The　conductivity　can　be　improved　by　increasing　the　welding　current.　However,　this　improvement　gradually　diminishes　with　increasing　pressure.　The　energy　dissipation　near　the　cathode　increases　with　pressure,　leading　to　further　contraction　of　the　arc.　The　reverse　plasma　jet　force　increases　with　pressure.　This　phenomenon　increases　instability　in　the　welding　process.　Clearly,　changes　in　arc　energy　transport　and　conductivity　have　crucial　effects　on　arc　stability.　In　conclusion,　increasing　the　arc　energy　input　or　reducing　the　arc　energy　dissipation　is　beneficial　for　suppressing　arc　contraction　and　improving　arc　stability.　©　2025　The　Society　of　Manufacturing　Engineers