The　pore　water　pressure　will　be　altered　with　the　changes　of　groundwater　characteristic　and　seepage　condition.　It　will　be　also　a　crucial　factor　to　the　bank　slope　instability.　Based　on　the　model　experiment　and　the　numerical　simulation　(EMU),　they　the　influence　of　drainage　velocity　on　the　bank　slope　stability　is　verified.　This　test　also　validates　that　the　siphon　drainage　technology　can　reduce　the　water　head　between　the　reservoir　and　groundwater　in　the　bank　slope　and　make　seepage　path　better.　The　results　will　be　useful　in　engineering　practice.