To　provide　microbial　evidence　for　technique　improvement　of　anaerobic　baffled　reactor　(ABR)　-　integrated　oxidation　ditch　-　biological　aerated　filter　(BAF)　combined　processes　for　landfill　leachate　treatment,　microbial　community　structure　of　the　treatment　system　under　different　recycle　ratios　were　investigated　by　polymerase　chain　reaction-denaturing　gradient　gel　electrophoresis　(PCR-DGGE)　combined　with　sequencing　and　phylogenetic　analysis.　The　results　indicated　that,　under　high　recycle　ratio,　microbial　community　structure　changed　slightly　along　with　reactor　and　running　time,　and　microbial　community　diversity　in　the　anaerobic　part　of　ABR　had　no　significant　change,　but　reduced　in　the　anoxic　part　of　ABR,　oxidation　ditch　and　BAF　with　the　increase　of　recycle　ratio.　Sequencing　results　revealed　that　there　may　be　other　denitrification　modes　of　autotrophic　denitrification　and　anaerobic　ammonia　oxidation　in　ABR　besides　conventional　biological　denitrification.　It　concluded　that　the　systemic　population　diversity　indexes　decreased,　and　the　phase　separation　of　acidogenesis　and　methanogenesis　was　destroyed　longitudinally　down　the　ABR　with　high　recycle　ratio,　which　illustrated　the　decrease　of　running　stability　of　the　treatment　system.　The　results　provide　some　valuable　references　for　design　and　operation　of　the　treatment　system.　©　2011　IEEE.