The bacterial diversity of activated sludge from submerged membrane bioreactor (SMBR) was investigated. A 16S rDNA clonelibrary was generated, and 150 clones were screened using restriction fragment length polymorphism (RFLP). Of the screened clones,almost full-length 16S rDNA sequences of 64 clones were sequenced. Phylogenetic tree was constructed with a database containingclone sequences from this study and bacterial rDNA sequences from NCBI for identification purposes. The 90.6% of the clones wereaffiliated with the two phyla Bacteroidetes (50%) and Proteobacteria (40%), and 8-Proteobacteria accounted for 7.8%,28.1%, and 4.7%, respectively. Minor portions were affiliated with the Actinobacteria and Firmicutes (both 3.1%). Only 6 out of64 16S rDNA sequences exhibited similarities of more than 97% to classified bacterial species, which indicated that a substantialfraction of the clone sequences were derived from unknown taxa. Rarefaction analysis of operational taxonomic units (OTUs) clustersdemonstrated that 150 clones screened were still insufficient to describe the whole bacterial diversity. Measurement of water qualityparameter demonstrated that performance of the SMBR maintained high level, and the SMBR system remained stable during this study.