In　this　paper,　the　topography,　landscape　and　geological　conditions,　and　deformation　process　and　failure　characteristics　of　the　super-high　cut　slope　K227　along　the　expressway　from　Yongchun　to　Yongding　in　City　Longyan　of　China　were　described.　Simulation　and　quantitative　evaluation　of　the　deformation　development　of　the　slope　were　conducted　with　the　back　analysis　for　slope　stability,　the　strength　reduction　method　and　the　finite　element　modelling　of　excavation.　A　method　based　on　the　differential　data　of　stress　tensor　is　proposed　to　determine　the　relaxation　zone　due　to　excavation　and　to　explain　better　the　mechanism　of　unloading　relaxation　due　to　the　excavation　of　the　high　cut　slope.　The　numerical　simulation　faithfully　reproduced　the　process　and　trending　of　the　stress　adjustment,　plastic　yielding,　development　of　slip　surface　and　deformation　at　all　stages　of　the　slope　failure.　The　slope　stability　mildly　increased　in　the　unloading　rebound　stage,　linearly　reduced　in　the　shearing　failure　stage　and　abruptly　reduced　in　the　instability　stage.　The　numerical　results　demonstrated　that　the　disturbance　due　to　the　fast　excavation　led　to　the　potential　weak　layer　to　be　fully　exposed　and　cut　off　the　mechanical　support　at　the　toe　of　the　slope.　The　unloading　relaxation　and　the　weakened　strength　of　the　rock　and　soils　resulted　in　the　tension　crack　at　the　top,　the　shearing　creep　of　deep　weak　layer　and　the　shearing　along　the　joints　at　the　toe　of　the　slope.　The　intermittent　rainfall　which　increased　the　weight　of　the　rock　and　soils　and　the　extra　pore　water　pressure　caused　the　slope　to　slide　intermittently.　The　slope　is　close　to　the　limit　equilibrium　state　globally　and　the　stability　may　be　abruptly　reduced　if　further　excavation　or　strong　rainfall　happen.　Finally,　the　discussions　and　reflections　on　the　emergency　and　rescue　strategy,　the　planning　of　slope　disaster　mitigation　methods　and　route　adjustment　are　also　presented.　©　2017,　Science　Press.　All　right　reserved.