Purpose:　This　research　was　to　reveal　the　thermal　characteristics　of　a　water-cooled　microwave　ablation　antenna　in　phantom,　and　the　influence　of　cooling　water　velocity　on　ablation　pattern　by　numerical　method.　In　addition,　by　comparing　the　numerical　results　with　experimental　results,　the　experimentally　obtained　SAR　was　proven　to　be　correct.　Methods:　The　temperature　distribution　in　ablations　was　simulated　by　the　finite　element　method.　In　the　FEM,　the　cooling　effect　in　the　region　of　the　water-cooled　antenna　was　introduced　by　applying　the　convective　coefficient　to　the　related　boundaries,　and　the　experimental　determined　SAR　in　phantom　was　applied　as　heat　generation　of　microwave　generator.　To　study　the　effect　of　water　flow　rate　on　ablation　pattern,　three　different　water　velocities　were　chosen.　In　addition,　the　phantom　thermal　properties　changes　were　considered　in　simulation　when　the　heating　temperature　was　above　80C.　Results:　The　ablation　pattern　could　be　identified　as　a　pear　shape.　The　temperatures　of　monitoring　points　which　were　located　near　the　antenna　could　rise　more　rapidly,　and　they　were　more　likely　to　achieve　steady　heat　transfer　state　within　a　short　time　compared　with　those　far　away　from　the　antenna.　The　cooling　water　effectively　decreased　the　temperature　near　the　antenna,　an　under-temperature　occurred　in　the　cooling　region,　and　the　different　cooling　water　flow　rate　did　not　affect　significantly　the　ablation　pattern.　Conclusions:　The　numerical　results　compared　reasonably　well　with　the　experimental　results　in　both　heating　pattern　and　temperature　of　individual　monitoring　point　over　the　same　heating　duration.　The　SAR　measured　by　our　previous　experiment　was　also　confirmed　by　this　numerical　simulation.　This　method　could　be　employed　to　study　combination　thermal　field　of　multi-antennas　in　future　work.