By　instruments　such　as　the　laser　power　meter,　the　beam　diagnosis　and　the　fast　CCD　camera,　the　effects　of　the　DC　TIG　arc　on　the　characteristics　of　a　vertically　incident　CO2　laser　beam　were　investigated.　The　experimental　results　demonstrate　that　part　of　the　laser　beam　energy　is　absorbed　by　the　arc　plasma.　This　absorption　increases　with　the　increase　of　the　arc　current　and　the　incident　laser　power,　and　becomes　more　evident　as　the　laser　beam　incident　position　is　closer　to　the　anode.　Meanwhile,　the　laser　beam　will　be　defocused,　deformed　and　deviated　to　the　cathode　due　to　the　arc　refraction.　The　beam　defocusing,　deformation　and　deviation　become　more　obvious　with　increasing　the　arc　current　and　the　incident　laser　power,　and　impinging　the　laser　beam　closer　to　the　anode.　The　combined　effect　of　the　absorption　and　defocusing　causes　the　power　density　decreases　sharply　as　the　beam　passes　through　the　arc.