Monitoring　data　over　the　years　have　shown　that　seasonal　rainfall　and　reservoir　level　changes　have　always　accompanied　the　accelerated　deformation　of　the　Xigouwan　landslide,　which　makes　it　difficult　to　identify　the　dominant　triggering　factors　of　landslide　deformation　and　poses　a　challenge　to　risk　analysis.　Given　this,　this　paper　analyzed　the　correlation　between　the　daily　deformation　rate　of　the　active　and　inactive　areas　in　the　Xigouwan　landslide　and　rainfall,　reservoir　level,　and　the　change　rate　of　reservoir　level　by　applying　the　attribute　reduction　algorithm　of　the　neighborhood　rough　set　model.　The　calculation　results　showed　that　the　deformation　in　the　active　area　was　mainly　affected　by　the　rainfall　in　the　past　seven　days.　It　was　also　related　to　the　short-term　change　rate　of　reservoir　water　level　in　some　ways.　The　weak　deformation　in　the　inactive　area　was　related　to　the　change　rate　of　reservoir　water　level　in　the　past　three　days.　Then,　based　on　the　landslide　deformation　characteristics,　it　was　further　obtained　that　the　average　rainfall　in　the　past　seven　days　inducing　severe　deformation　in　the　active　area　was　about　20　mm.　The　decline　of　the　reservoir　water　level　influenced　its　deformation,　but　the　effect　was　small.　The　reservoir　level　change　affected　the　weak　deformation　in　the　inactive　area　with　negligible　influence,　while　the　weak　deformation　in　the　inactive　area　was　mainly　influenced　by　the　reservoir　level　change.　Finally,　the　seepage-mechanics　numerical　analysis　of　the　Xigouwan　landslide　reveals　the　deformation　mechanism　of　the　active　area　under　long-duration　early　rainfall.　As　the　rainfall　intensity　increased　from　1　mm　/　d　to　20　mm　/　d,　the　pore　water　pressure　at　the　bottom　of　the　landslide　body　gradually　increased.　The　internal　reservoir　level　rose　and　extended　to　the　active　area,　which　caused　the　landslide　body　in　the　active　area　to　go　from　a　stable　state　to　an　under-stable　state,　leading　to　large　deformation　in　the　active　area.　In　addition,　the　numerical　simulation　results　further　showed　that　the　decline　of　the　reservoir　level　had　little　effect　on　the　internal　seepage　field　and　the　stability　in　the　active　area.　The　reservoir　level　change　greatly　influenced　the　internal　seepage　field　in　the　inactive　area,　indicating　that　the　weak　deformation　in　the　inactive　area　was　mainly　affected　by　the　reservoir　level　change.　The　complete　analysis　results　of　factors　inducing　the　Xigouwan　landslide　in　this　paper　can　help　provide　early　warning.　The　average　rainfall　of　20　mm　in　the　past　seven　days　can　be　used　as　one　of　the　early　warning　thresholds　for　severe　deformation　in　the　active　area　of　the　Xigouwan　landslide.　©　2023　Chinese　Academy　of　Geological　Sciences　Institute　of　Geomechanics.　All　rights　reserved.