To eliminate N₂O emission or utilize it for energy recovery, a laboratory-scale SBR inoculated with common activated sludge with acetate and nitrate additions decoupled, was conducted for endogenous denitrification running with anaerobic/anoxic cycles without DPAOs. During one cycle, approximately 50% of nitrate was converted to nitrite, N₂O emission rate increased with nitrite accumulation, and 2.04% of removed nitrogen was emitted as nitrous oxide (N₂O). Batch tests were conducted to compare the emission of N₂O that was influenced by external carbon source dosage (C/N was 0, 0.75 and 2.50) using nitrite as the electron acceptor before and after poly-β-hydroxybutyrate (PHB) was synthesized.The results showed that, the N₂O emission was slightly decreased with the increase of total carbon source, and the N₂O conversion ratio was between 0.24% and 1.61%. 15.90% of N₂O conversion ratio was obtained in the absence of external organic carbon, the maximum N₂O emission rate was 71.29 μg/(min·g), and the N₂O emission was 14-26 times higher than that of the other batch test results, indicating that when the PHB was the sole electron donor, the endogenous denitrification could produce more N₂O using nitrite as the electron acceptor.