To　investigate　bacterial　community　structure　and　biodiversity　of　a　CANON　reactor　that　was　operated　stably　at　room　temperature,　total　DNA　was　extracted　from　the　biofilm　for　PCR-DGGE　analysis.　The　results　of　microbial　community　analysis　showed　that　the　ammonia　oxidizing　bacteria　Nitrosomonas　and　Nitrosospira,　together　with　the　anaerobic　ammonia　oxidizing　bacteria　Candidatus　Brocadia　and　Candidatus　Kuenenia　were　detected　as　the　functional　bacteria　while　nitrite-oxidizing　bacteria　(NOB)　was　not　found　in　the　CANON　system,　and　the　biodiversity　of　AOB　was　significantly　higher　than　anammox　bacteria.　Besides,　some　other　bacteria　like　Shewanella,　Pseudomonas,　Ignatzschineria,　Dechloromonas　and　some　uncultured　bacterium　related　to　Clostridia,　α-Proteobacteria　and　Bacillales　also　existed　in　the　reactor.