In　the　research　of　the　data　envelopment　analysis　method,　when　the　input　and　output　value　of　the　decision　making　unit　is　interval　number,　the　calculation　of　the　relative　interval　efficiency　depends　on　the　choice　of　the　front　face　of　the　production.　Therefore,　by　the　comparison　of　the　interval　model　of　slack　based　model(SBM)　under　different　production　frontier,　it　is　concluded　that　it＇s　most　favorable　for　the　decision　making　unit　ranking　by　the　interval　efficiencies　which　are　calculated　both　by　the　best　production　frontier.　Then,　the　interval　number　similarity　theory　is　introduced,　and　the　fuzzy　similarity　matrix　of　interval　efficiency　is　established.　The　reference　interval　efficiency　unit　similarity　method　is　proposed,　which　is　used　to　cluster　and　sort　the　decision　making　units.　Finally,　a　numerical　example　is　given　to　illustrate　the　feasibility　and　effectiveness　of　the　proposed　methods.　©　2017,　Editorial　Office　of　Control　and　Decision.　All　right　reserved.