A　type　of　supersonic　separation　structure　is　designed　according　to　natural　gas　field　condition　and　gas　well　drilling　technology　parameters.　Based　on　the　new　device,　a　reasonable　three-dimensional　CFD　model　is　established,　and　the　realizable　k-ε　turbulence　model　is　selected　to　simulate　the　internal　flow　field　of　the　supersonic　separator.　The　separation　parameters　such　as　pressure,　temperature,　Mach　number,　and　turbulence　kinetic　energy　along　the　axis　inside　the　supersonic　separator　are　investigated,　the　flow　characteristics　along　the　radial　direction　in　different　sections　are　also　discussed.　The　simulation　results　show　that　when　the　pressure　loss　ratio　is　47.5%,　the　shock　wave　will　occur　in　divergent　of　the　Laval　nozzle　(about　98　mm　from　the　entrance　of　the　supersonic　separator).　Due　to　the　expansion　effect　of　the　Laval　nozzle,　the　lowest　temperature　will　achieve　190.52　K.　The　calculation　result　agrees　well　with　the　previous　experimental　result.　The　new　separator　structure　can　also　produce　strong　swirling　intensity.　Besides　the　calculation　method　gives　a　good　guidance　for　the　optimal　design　of　the　supersonic　separator　dimensions.