Abstract: This paper summarized the microbiology progress of phosphorus accumulating organisms ( PAOs) in enhanced biological phosphorus removal ( EBPR ) system， introduced the involved PAOs species classification and biological characteristics and concluded the techniques for identifying PAOs microbiology，including traditional pure culture technology， staining and microscope technology， modern molecular with extensional techniques and the combination of various technologies; the application of molecular techniques was analyzed． This study mainly introduced the progress of accumulibacter morphology and metabolic characteristics， and discussed the study and developing direction of PAOs microbiology in the future．