Based on the purified DNA extracted directly from water samples and marine sediment samples from Laizhou Bay,16 S rDNA fragments of bacteria were PCR amplified and 16 S rDNA clone libraries were constructed.The sequenced clones of sediment fell into two phylums of Proteobacteria and Bacteroidete while the Proteobacteria was the dominant group and the subgroup of α-Proteobacteria,γ-Proteobacteria and y-Proteobacteria predominated in them with 38.7%,3.2%,and 41.9%respectively.The sequenced clones of water fell into nine phylums including Proteobacteria,Acidobacteria,Verrucomicrobial,Plancomycene,Bacteroidetes,Firmicutes,Lentisphaeria,Chlorobi,and Nitrospira while the Proteobacteria was the dominant group and the subgroup of crProteobacteria,y-Proteobacteria and y-Proteobacteria predominated in them with 11.8%,23.5%,and 41.9%,respectively.