In　order　to　investigate　the　influence　of　nozzle　ablation　to　arc,　a　2-D　axisymmetric　magneto-hydro-dynamics　arc　model　is　developed　to　simulate　the　arc　behavior　during　the　whole　interruption　process　in　a　puffer-type　high　voltage　circuit　breaker,　considering　the　nozzle　ablating　and　the　mixing　process　of　Polytetrafluoroethylene　(PTFE)　vapor　with　SF6.　The　results　show　that　the　arc　radius　firstly　increases　and　then　decreases　as　arc　current　varies　according　to　its　sinusoida　waveform.　At　3.5　ms　after　arc　initiation　the　nozzle　ablation　starts,　and　2.5　ms　later　the　current　nearly　reaches　its　peak　value　and　nozzle　ablation　develops　intensely.　Meanwhile　the　nozzle　is　blocked　by　arc　at　this　time　and　consequently　the　vapor　concentration　in　nozzle　reaches　the　highest.　Then　while　the　current　decreasing　and　open　distance　increaseing　the　vapor　concentration　gradually　decreases.　Before　current　zero　the　extinction　peak　of　arc　voltage　occurs.　It　indicates　that　the　PTFE　vapor　enhances　pressure　rise　in　arc　quenching　chamber　and　strengthens　the　arc　blocking　effect　on　nozzle;　the　arc　radius　is　wider　and　arc　temperature　is　lower　when　nozzle　ablation　is　considered.