In　the　present　paper,　a　water-cooled　copper　anode　was　designed.　The　radial　distribution　of　arc　column　that　after　plasma　arc　penetrated　the　work-pieces　was　measured.　The　effects　of　welding　current　and　ambient　pressure　on　plasma　penetrating　arc　pressure　was　studied.　The　experiment　results　refer　that　arc　pressure　of　central　area　of　arc　column　is　maximum,　which　decreases　rapidly　along　the　radial　from　the　center　to　the　edge　of　arc　column.　The　arc　pressure　increases　with　the　increasing　welding　current　in　the　same　ambient　pressure.　Within　a　certain　range　of　pressure,　the　arc　pressure　increases　significantly　with　the　deceasing　ambient　pressure　in　the　same　welding　current.　The　change　of　ambient　pressure　has　a　more　significant　influence　on　arc　pressure　than　the　change　of　welding　current.　©　2016,　Editorial　Board　of　Transactions　of　the　China　Welding　Institution,　Magazine　Agency　Welding.　All　right　reserved.