For　the　purpose　of　knowing　the　motion　law　of　sand　erosion　and　improving　the　efficiency　of　cyclone　separation　sand　sampler,　the　finite　element　model　of　cyclone　separation　sand　sampler　is　built　by　using　the　software　of　Fluent.　There　is　a　two-phase　movement　inside　the　cyclone　separation　sand　sampler,　including　air　and　soil　particles.　The　cyclone　separation　sand　sampler　mainly　separates　the　soil　particles　from　the　air.　Since　the　concentration　of　the　soil　particles　is　not　too　high,　its　movement　inside　the　sand　sampler　depends　largely　on　the　gas　phase　(air)　movement,　and　a　majority　of　the　particles　flow　with　the　air.　Due　to　the　above-mentioned　reasons,　it　is　necessary　to　make　further　analysis　on　the　air　flow　inside　the　cyclone　separation　sand　sampler.　Boundary　conditions　are　of　great　importance　to　the　simulation　of　the　gas　flow　inside　the　cyclone　separation　sand　sampler,　and　the　gas　phase　has　been　simplified:　the　gas　in　the　sand　sampler　is　air,　with　a　density　of　1.225　kg/m3　and　a　viscosity　of　18.1×10-6;　it　is　treated　as　incompressible　gas,　and　its　flow　is　treated　as　in　steady　state;　the　exit　is　set　for　free　outflow;　the　wall　surface　is　set　as　no　skidding　and　no　moving　surface;　the　2　surfaces　overlapped　by　the　ascension　pipe　and　the　barrel　of　the　sand　sampler　are　set　respectively　as　Interface　for　data　exchange;　the　upper　part　of　the　sand　sampler　and　the　sandbox　are　sealed　well,　without　gas　flowing　out;　the　straight　pipe　connecting　the　cone-shaped　part　and　the　sandbox　is　10　mm　long;　the　hydraulic　diameter　is　0.015　mm,　the　Reynolds　number　is　1.02×104　and　the　turbulent　intensity　is　5.1%.　Based　on　the　RNG　k-Ε　model　and　the　Reynolds　stress　model,　numerical　analysis　is　carried　out　for　the　cyclone　separation　sand　sampler.　Besides,　some　wind　tunnel　tests　are　made　for　3　cyclone　separation　sand　samplers　with　different　structure　parameters.　The　internal　motion　law　of　the　gas　phase　is　found　through　the　finite　element　analysis;　current　field　intensity　near　the　gas　exit　tube　of　the　sand　sampler　is　stronger　and　the　＇shunting　flow＇　exist　inside.　At　the　same　time,　by　the　numerical　simulation　of　3　cyclone　separation　sand　samplers　with　different　structure　parameters,　the　results　show　that　the　sand　sampler　with　cylinder　diameter　of　50　mm,　and　cone　height　of　125　mm　has　the　smaller　turbulent　kinetic　energy　0.99　m2/s2　and　the　maximum　upward　axial　velocity　1.48　m/s　in　sandbox　bottom.　In　addition,　the　wind　tunnel　test　is　done　with　3　different　structural　parameters　of　the　cyclone　separation　sand　sampler,　and　the　experimental　results　show　the　turbulent　kinetic　energy　of　sandbox　bottom　which　has　certain　impact　on　the　trapping　efficiency　is　changed　with　cylinder　diameter　and　cone　segment　height.　Compared　to　cylinder　diameter,　cone　segment　height　has　greater　influence　on　the　efficiency　of　the　cyclone　separation　sand　sampler.　The　cyclone　separation　sand　sampler　has　better　separation　performance　and　higher　trapping　efficiency　when　the　turbulent　kinetic　energy　and　the　upward　axial　velocity　of　sandbox　bottom　are　lesser.　Through　numerical　simulation　and　wind　tunnel　test,　the　objective　function　is　determined　by　the　turbulent　kinetic　energy　and　the　upwards　axial　velocity　of　the　bottom　of　sandbox.　The　length　of　the　straight　tube　of　sandbox　is　optimally　designed　through　the　objective　function.　The　efficiency　of　cyclone　separation　sand　sampler　can　be　improved　while　the　straight　pipe　of　sandbox　is　16　mm.　The　results　can　provide　the　basis　for　further　enhancing　the　performance　of　cyclone　separation　sand　sampler.　©,　2015,　Chinese　Society　of　Agricultural　Engineering.　All　right　reserved.