Abstract: To explore the ability of accumulation of endogenous polymers and denitrification characteristics driven by endogenous polymers of microorganisms acclimated by aerobic/anoxic F/F (O/A-F/F) mode, and compare with traditional aerobic F/F (O-F/F) mode, sewage wastewater added with acetate as carbon source was used in this study. The F/F=0.1 was applied to acclimated activated sludge by O/A-F/F and O-F/F modes. The abilities of acclimated microorganisms under two modes were compared. Results show that the PHA yield of O/A-F/F and O-F/F modes is 0.52 and 0.78, respectively. Although the PHA yield under O/A-F/F mode is lower, the function of denitrification driven by PHA can be achieved. The specific denitrification rate is 2.76 mg/(h·g). The denitrification stoichiometric coefficient is 2.0 mol PHA per mol NO₃^--N. Betaproteobacteria, unclassified Bacteroidetes, lgnavibacteria and Bacteroidia are dominant microorganisms after selection by O/A-F/F mode while Betaproteobacteria, Flavobacteria, Alphaproteobacteria and Gammaproteobacteria are dominant microorganisms under O/-F/F mode. The organic matter can be stored as endogenous polymers under O/A-F/F mode during aerobic and be applied to driving denitrification during anoxic achieved.