Abstract: The population structure of the phosphate dissolving bacteria(PDB)in the Donghu Lake was studied.66 PDB strains, including 27 strains of organic phosphate dissolving bacteria(OPB), 23 strains of inorganic phosphate dissolving bacteria(IPB)and 16 strains with both functions, were isolated from Stations Ⅰ, Ⅱ, and Ⅲ of the Donghu Lake. According to their morphological, physiological and biochemcal properties, they should belong to 15 bacterial genera, namely: Bacillus, Micrococcus, Aeromonas, Achromobacter, Acinetobacter, Alcaligenes, Brevibactcrium, Beneckea, Enterobacter, Flavobacterium, Microbacterium, Pseudomonas, Serratia. Xanthomonas, and Zymomonas, apart from 3 unidentified strains.The species composition of PDB in the 3 sampling stations was quite different. 11 genera were isolated from Station Ⅰ, 8 genera from Station Ⅲ, and only 3 genera were found from Station Ⅱ. Bacillus and Micrococcus are the dominant genera of PDB in this lake.The amount, species composition and distribution of PDB vary with the degree of pollution and the content of phosphate compounds in the water column and the bottom deposit. There are much more PDB in sediments than in water columns The polluted Station Ⅰ contains more PDB. In most cases the number of OPB overrun that of IPB.