To realize the stable and efficient operation of biogas digester in cold region, a combined regulation technique of microbial community should be established. The microbial community in the largest full-scale digester of Hailin Farm was investigated using 454 pyrosequencing technology and PCR-DGGE. The massively parallel sequencing technology was used to measure bacterial diversity of biogas slurry during a stable operation. A total of 1297 sequences were obtained, and the dominant bacteria were Firmicutes, Bacteroidetes and Proteobacteria, which accounted for 46.39％, 21.41％ and 18.98％, respectively. At genus level (the relative abundances>5.0％), Proteiniphilum, Spirochaeta and Wolinella were the abundant taxa. The diversities of methanogen were analyzed using PCR-DGGE, and the detected archaea were Methanocorpusculum sp., Methanosaeta sp., Methanobacterium sp. and Methanosarcina sp.. Notably, the methane produced by acetoclastic methanogens, and dominant fermentative bacteria during the hydrolysis and acidogenesis were detected form animal digestive system.