It was studied for community structure of microorganisms in the phosphorus removal processes under the circulating situation, and analyzed for microorganism's structure and behavior characteristics by the molecular biology technique with direct obtaining of DNA from samples of activated sludge, and by nested PCR and DGGE. It was also determined community structure of microorganisms. It was analyzed structures of Proteobacteria and Acidobacterium by 16S rDNA V3 area gene fragments sequences in activated sludge. By comparing gene sequences in the National Center of Biological Information (NCBI), were determined the kinds of part of microorganisms. Analyzing the low of changes of preponderant bacteria in anaerobic/aerobic and anaerobic/anoxic conditions takes to know, that under the stable situation of phosphorus removing, the system of microorganism's structure can kept mostly constant. Minority races that have changed in amount or kind has something to do with the variation of oxygen level in the system, but structure totally can adapt the environmental conditions of the processes, while it placed in dynamic varieties.