Fine　particles　endanger　our　health　and　the　environment　seriously.　The　concentration　of　fine　particles　in　the　flue　gas　after　the　wet　flue　gas　desulfurization　system　increases　instead　of　decreasing.　Wet　phase　transition　agglomeration　technology　is　the　newest　way　to　remove　the　fine　particles　in　the　flue　gas.　Considering　the　velocity　difference　of　particle　agglomeration　and　growth　triggered　by　the　properties　of　various　particles　and　the　speed　difference　between　particles　and　carrier　gas,　this　paper　improved　the　particle　agglomeration　equation　and　established　mathematics　model　of　particle　agglomeration　and　growth.　Thereafter,　a　two-layer　cyclone　device　was　installed　in　the　normal　growth　tube　to　increase　the　centrifugal　force　of　particles　and　the　turbulence　intensity　of　flue　gas.　Besides,　simulation　of　flow　fields　of　the　normal　growth　tube　and　the　improved　one　was　implemented　respectively　through　CFD　method.　It　is　indicated　that　the　simulation　of　particle　agglomeration　and　growth　in　the　growth　tube　with　the　improved　mathematical　model　has　a　higher　accuracy.　Actually,　the　simulation　accuracy　reaches　88.2%　compared　with　the　experimental　result,　which　is　enhanced　by　11.3%　based　on　the　previous　models.　Flue　gas　in　the　growth　tube　with　cyclone　device　not　only　stays　for　a　longer　time　than　that　in　a　normal　growth　tube,　but　also　gets　higher　and　homogeneous　degree　of　supersaturation　which　facilitates　the　agglomeration　and　growth　of　particles.　Moreover,　the　removal　efficiency　of　fine　particles　number　concentration　is　up　to　65.8%　with　the　improved　growth　tube.　©　2021,　Science　Press.　All　right　reserved.