Supersonic　separator　is　a　new　technology　based　on　the　adiabatic　expansion　of　swirling　gas　flow,　and　at　present　it　has　demonstrated　great　application　potential　in　separating　and　processing　droplet　liquid　contained　in　natural　gas.　However,　its　coefficient　of　performance　is　still　low　and　there　seems　to　be　a　large　gap　in　the　method　that　evaluates　the　separation　efficiency　in　a　satisfactory　manner.　In　order　to　promote　the　wide　application　of　this　technology　in　the　dehydration　field,　it　is　necessary　to　find　a　new　and　feasible　approach　that　can　be　used　to　predict　the　flow　characteristic　and　separation　performance　inside　a　supersonic　separator.　In　this　paper,　a　comprehensive　three-dimensional　fluid　numerical　model　to　study　the　flow　behavior　and　separation　efficiency　in　a　supersonic　separator　was　established　coupled　with　the　discrete　particle　model　(DPM).　The　mixture　of　air　and　water　droplets　was　chosen　as　working　fluid.　The　gas　phase　was　modeled　with　compressible　Navier-Stokes　equations　for　two-phase　flow　and　the　RSM　turbulence　model　was　taken　into　account.　The　droplet　phase　was　modeled　with　the　discrete　particle　model　(DPM),　in　which　the　droplets　are　assumed　to　have　the　same　sphere　shape　and　ignore　the　phase　transition　and　nucleation　process.　A　pilot　test　facility　was　carried　out　to　validate　the　numerical　model.　The　experimental　results　not　only　indicate　that　the　new　dehydration　device　can　efficiently　separate　the　liquid　droplets　from　wet　gas,　but　also　prove　that　the　numerical　results　were　great　agreements　with　the　experimental　results.　Furthermore,　based　on　the　proposed　numerical　approach,　the　gas-droplet　turbulent　flow　structures　were　predicted,　the　effects　of　different　structure　parameters　and　operation　conditions　on　the　separation　efficiency　were　also　investigated.　The　current　works　settle　a　foundation　for　further　explorations　on　the　supersonic　gas-liquid　separation　flows　inside　a　supersonic　separator　as　well　as　the　possible　new　applications.