The　biofilm　system　is　beneficial　for　Anammox　process　designed　to　treat　landfill　leachate.　In　this　study,　the　composition　of　extracellular　polymeric　substances　(EPS)　and　the　microbial　community　in　an　Anammox　biofilm　system　were　analyzed　to　determine　the　functions　driving　the　biofilm＇s　ability　to　treat　landfill　leachate.　The　results　demonstrated　that　increasing　influent　carbon　oxygen　demand　(COD)　could　stimulate　EPS　production.　EPS　helped　enrich　Anammox　bacteria　and　supplied　them　with　nutrients　and　enzymes,　facilitating　effective　nitrogen　removal　(approximately　95%).　The　variation　in　Anammox　bacteria　was　similar　to　the　variation　in　EPS　composition.　In　the　tested　Anammox　Sequencing　Biofilm　Batch　Reactor　(SBBR)　system,　Candidatus　Kuenenia　was　dominant　among　known　Anammox　genus,　because　of　its　high　substrate　affinity　and　because　it　adapts　better　to　landfill　leachate.　The　relative　abundance　of　Candidatus　Kuenenia　in　the　biofilm　rose　from　3.26%　to　12.38%,　illustrating　the　protection　and　enrichment　offered　by　the　biofilm　in　carrying　out　Anammox.