Cyanobacterial bloom has been a hot issue and the microbial community is one of the important functional groups in the decomposition process of cyanobacteria accumulation.In this study,restriction fragment length polymorphism(RFLP)was applied to analyze the bacterial diversity of different depths in the cyanobacterial accumulation of lakefront at northern shore of west region of Chaohu Lake.The total DNA of the microorganisms from three different layers of cyanobacterial accumulation(Layer A:0-2 cm,Layer B:2-10 cm,Layer C:10-20 cm)were extracted by the direct method.The DNA extracted was amplified using bacterial universal primers 27F and 1492R.PCR products were ligated into the pMD-18T Vector and ligations were transformed into Escherichia coli DH5α to construct 16S rDNA clone library of microbes in the cyanobacterial accumulation.120 positive clones each layer from the library were screened and their 16S rDNA fragments were reamplified.The fragments were digested with HhaⅠ and RsaⅠ respectively and their fingerprints were analyzed.The results showed that the layers from top to bottom include 51,32,27 restriction endonnuclease types and the coverage(C- value)of the clone library were 80.8%, 87.5%, 89.2%, respectively.Margalef indices(d_Ma), Shannon-Wiener indices(H)and Simpson indices(D)all decreased with the depth increasing.Phylogenetic analysis suggested that the dominant bacteria in different layers of cyanobacterial accumulation belonged to Firmicutes and Proteobacteria.With the depth increasing,the species of Proteobacteria decreased,but those of Firmicutes increased.Some bacterial species in Layer A also belonged to Cyanobacteria,Actinobacteria,Planctomycete,and Spirochaetes.And some in Layer C belonged to Bacteroidetes.The results revealed the changes of bacterial diversity and species composition during the decomposition of cyanobacteria accumulation.This study on the bacterial diversity not only provided microbiology information for understanding the decomposition process of cyanobacteria accumulation,but also supplied the theoretical basis for using the resources of unknown bacteria in the cyanobacteria accumulation.