Karst　tiankeng　is　a　special　grand　negative　landform.　The　environment　of　tiankeng　inside　are　independent　of　that　outside,　showing　a　unique　characteristics　of　plant　community.　Taking　a　moderately　degraded　tiankeng　with　good　accessibility,　Bajiaxiantang　as　the　focus,　the　dominant　species　with　importance　value　>1　were　selected　to　clarify　the　interspecific　association　of　11　dominant　species　by　the　multi-disciplinary　approach　including　the　variance　ratio　(VR)　of　overall　association,　χ2　test,　association　coefficient　(AC)　and　Spearman　rank　correlation　coefficient.　The　results　showed　that　VR　of　overall　association　in　this　grassland　community　was　1.377　(which　was　larger　than　1),　indicating　that　this　community　had　overall　significantly　positive　interspecific　association.　Given　the　great　difference　between　the　positive　and　negative　association　and　significantly　negative　correlation　between　heliophiles　and　sciophiles,　the　community　had　independent　distribution.　The　number　of　positive　pairs　of　species　(26)　was　less　than　that　with　negative　correlation　(29)　in　Spearman　correlation　analysis.　Combined　with　the　difference　of　tiankeng＇s　micro-environment,　dominant　plant　species　of　degraded　tiankeng　could　be　divided　into　three　ecological　groups.　The　grassland　community　in　tiankeng　showed　circle　distribution　pattern.　©　2018,　Science　Press.　All　right　reserved.