Karst　tiankengs,　as　one　of　the　most　magnificent　negative　topographies,　are　capable　of　forming　a　bank　for　species　diversity　conservation　easily.　More　than　300　karst　tiankengs　have　been　discovered　and　identified　worldwide.　Given　its　treacherous　terrain,　although　original　karst　tiankeng　were　identified　as　species　refuges,　the　broader　distribution　of　degraded　karst　tiankeng　has　not　been　systematically　studied.　Our　study　area　comprised　the　degraded　karst　tiankeng　cluster　immersed　in　the　fragmented　karst　forests　of　Yunnan,　China.　Fifty-eight　plant　samples　were　selected　from　karst　tiankengs　and　surface.　We　compared　species　composition,　and　analyzed　diversity　indices　and　similarity　coefficients　to　verify　the　isolation　effect　of　karst　tiankengs　on　floras.　The　results　indicated　that:　(1)　In　the　degraded　karst　tiankeng,　there　were　24　families,　37　genera　and　48　species　in　the　tree　layer　and　27　families,　43　genera　and　49　species　in　the　shrub　layer.　Outside　the　degraded　karst　tiankengs,　20　families,　31　genera　and　39　species　were　in　the　tree　layer,　and　the　shrub　layer　included　26　families,　44　genera　and　55　species.　(2)　The　species　composition　reached　significant　differences　within　and　outside　degraded　karst　tiankeng　(p　＜　0.05)　based　on　the　analysis　of　variance　(ANOVA).　(3)　In　the　degraded　karst　tiankeng,　species　richness/diversity　in　trees　were　higher　than　those　in　the　shrub　layer,　while　at　the　surface,　shrubs　had　higher　richness　and　lower　diversity　than　trees　by　Alpha-diversity　index.　And　for　Beta-diversity　index,　species　similarity　among　degraded　karst　tiankengs　(0.215)　was　extremely　dissimilar,　which　was　even　lower　than　the　contrast　within　and　outside　the　degraded　karst　tiankengs　(0.272).　(4)　Shared　species　ranged　from　1　to　5　among　the　four　habitats,　with　high　variability　in　plant　species　across　the　habitat　matrices.　Through　a　comparative　analysis　of　systematic　biodiversity　methods,　we　found　that　the　degraded　karst　tiankengs,　an　independent　type　of　karst　tiankeng,　are　the　unreported　refugia.　Species　records　in　degraded　karst　tiankeng　cluster　will　contribute　to　plant　diversity　conservation　and　resource　management,　and　to　the　linkage　with　broader　China＇s　karst　floras.　Karst　tiankeng　botanical　habitats　possess　not　only　biodiversity　value　for　in　situ　conservation,　but　will　further　support　the　ecological　recovery　of　surface　flora.　While　its　mechanism　needs　to　be　further　revealed.