The average contents of total phosphorus and active phosphorus concentration were 0.113mg/L and 0.011mg/L, respectively; the inorganic phosphorus-degrading bacteria and organic phosphorus-degrading bacteria in the sediment was 6.73×10⁵ cells/g dry sediment, but it was only 71cells/g in the water, and there was also significant temporal and spacial difference. According to the bacteria group's shape, 3 representative inorganic phosphorus-degrading bacteria and 7 dominant organic phosphorusdegrading bacteria were isolated. Identification showed that the 3 representative inorganic phosphorus-degrading bacteria were similar to Bacillus megaterium, Pseudomonas sp. and Paenibacillus sp. The 7 dominant organic phosphorus-degrading bacteria were similar to Bacillus thurigiensis, Bacillus pumilus, Bacillus sp., Bacterium sp., Microbacterium oxydans, Bacillus cereus and Bacillus simples. The phosphorus-degrading bacteria of Lake Taihu were classified into Bacillus and Pesudomonas. The contribution of inorganic phosphorus-degrading bacteria for the aquatic bioavailable phosphorus was greater than that of organic phosphorus-degrading bacteria.