Abstract: The influence of different volume ratio on pollutants removal was studied. The optimal effluent performance of COD,NH₄⁺-N,TN and TP were 28.12,0.58,9.26 and 0.43 mg/L,respectively,with anaerobic/anoxic/oxic volume ratio of 4:8:10. More than 72% of carbon sources were utilized effectively for phosphorus release and denitrification,and about 12.6% of TN was removed through simultaneous nitrification and denitrification(SND) in oxic zones. The experimental results also indicated that the volume ratio had no distinct effect on COD and NH+ 4-N removal,but had distinct impact on TN and TP removal. At the same time,with the strategy that reduce the volume of the aerobic zone to improve the anoxic volume, the autotrophic bacteria could take full advantage of more carbon sources for denitrification and phosphorus release in each anoxic or anaerobic zone,and which was also conducive to enrich denitrifying poly-phosphate accumulating organisms(DPAOs). The highest proportion of DPAOs was 20.9%.