Taking　the　karst　collapse　in　Zhangkeng　Village　of　Yongding　County　in　Fujian　province　as　the　research　object,　the　mechanism　of　karst　collapse　was　summarized　based　on　field　investigation　with　the　geological　environment　features　and　geotechnical　data.　Furthermore,　the　mechanical　model　considering　negative　pressure,　buoyancy　and　dynamic　pressure　of　underground　water　as　well　as　rainfall　infiltration　was　built　by　using　the　Mohr-Coulomb　criterion.　The　stability　analysis　of　the　cave　was　carried　out　by　the　limit　equilibrium　theory,　and　the　finite　difference　soft-ware　FLAC3D　was　used　to　simulate　the　developing　process　of　karst　collapse.　The　research　results　show　that　the　collapse　mechanism　of　the　karst　collapses　occurred　in　Zhangkeng　Village　of　Yongding　County,　Fujian　province　is　seepage　erosion　and　the　coefficient　of　collapse　is　proportional　to　the　underground　water　level.　The　decrease　of　underground　water　level　occupies　an　important　position　to　the　cause　of　karst　collapse　in　comparison　with　pressure　difference　and　precipitation　intensity.　The　karst　collapses　are　mainly　caused　by　the　excessive　drainage　of　the　surrounding　mine,　which　induced　rapid　decline　in　groundwater　level　and　strong　suffosion.　©　2018　Science　Press.