In　this　paper,three　different　siphon　pipelines　were　imported　to　the　CFD　software　FLUENT　with　the　gas-liquid　two-phase　flow　field　to　simulate　the　flush　process　and　study　how　the　siphon　pipeline　structures　affected　the　siphon　performance.By　changing　some　design　parameters　of　the　pipeline　structures,including　the　inclined　angle　of　resistant　section　and　the　length　of　upward　section,numerical　simulation　results　were　analyzed　and　some　valuable　guidelines　for　optimizing　the　siphon　pipeline　structures　was　proposed.The　simulation　results　indicated　that　the　tip　pipelines　have　an　obvious　negative　pressure　in　the　three　types　of　siphon　pipelines　which　is　important　to　start　the　siphon　phenomena.A　positive　pressure　is　generated　at　the　outlet　of　the　pipelines,accompanied　with　violent　gas　and　liquid　phase　changes.Properly　shortening　the　length　of　the　upward　section　may　prolong　the　duration　of　siphon.Through　increase　of　the　inclined　angle　of　resistant　section,the　stability　of　the　siphon　would　be　more　stable.siphon　pipeline;　gas-liquid　two-phase　flow;　numerical　simulation;　siphon　performance;　optimal　design　©　2018,　Editorial　Office　of　Chinese　Journal　of　Computational　Mechanics.　All　right　reserved.