Based　on　field　tests　on　19　groups　of　data　and　phenomenon　analysis　of　inrush　or　bursting　waste　from　karst　cavity　of　Maluqing　tunnel　of　Yichang-Wanxian　Railway,　a　conceptual　model　of　karst　water　burst　flood　(KWBF)　is　proposed　by　means　of　statistical　analysis　and　phenomenological　induction.　Through　analyzing　its　characteristics　during　different　construction　stages,　it　is　shown　that　KWBF　has　the　delay　characteristics.　The　time　history　analysis　of　the　karst　water　burst　flood　shows　that　because　of　pressure　dispersion　between　inside　and　outside　of　the　cavity,　seepage　enlargement　is　evolved　into　conflux　so　as　to　deprive　groundwater　from　aquifer　aqueduct　and　fracture,　and　the　water　together　with　mud　suddenly　releases　from　karst　into　the　tunnel.　The　key　factor　for　the　delay　characteristic　of　KWBF　is　water　amount　and　silt　or　filling　degree　of　conflux　aqueduct.　The　delay　time　of　KWBF　on　supply　air　continuously　reduces　the　response　time,　according　to　which　the　possibility　of　KWBF　is　reduced.　Forecasting　of　KWBF　is　conducted　by　use　of　the　rainfall　seeping　theory　and　statistical　analysis　method.　The　basic　data　are　obtained　from　field　quantity　observation　such　as　rainfall　and　hydrograph　measurement.　The　control　index　of　safe　operation　during　the　rescue　and　discharge　period　is　proposed.