Abstract: Shortcut nitrification, as one of the key technologies for achieving carbon emission reduction and energy conservation, had gradually been applied in municipal wastewater treatment. To investigate nitrogen and oxygen migration-transformation characteristics during the NH₄⁺-N→NO₂⁻-N oxidation stage in urban sewage short-cut nitrification processes, an intermittent aeration strategy （aeration/rest duration ratio of 30 min:30 min） was adopted to achieve rapid start-up and stable operation of shortcut nitrification （room temperature operation with DO maintained at 1~1.2 mg/L）. Results demonstrated that the ammonia nitrogen removal efficiency exceeded 98% and nitrite accumulation rate surpassed 97% in domestic wastewater treatment. The δ¹⁵N_NO2 and δ¹⁸O_NO2 values increased with enhanced NO₂⁻-N accumulation rate, where δ¹⁸O_NO2 gradually stabilized at 11‰ while δ¹⁵N_NO2 rose from −25.79‰ to −12.51‰, indicating significantly stronger nitrogen isotope fractionation than oxygen isotope fractionation. Through artificial regulation of δ¹⁸O_H2O levels （54.34‰, 97.98‰, and 147.19‰）, δ¹⁸O_NO2 abundance was observed to substantially exceed δ¹⁸O_H2O values with increasing NO₂⁻-N accumulation rate, confirming that both O₂ and H₂O participated in NH₄⁺-N to NO₂⁻-N conversion during shortcut nitrification. The dual N and O isotope fractionation technology provided in-depth insights into the formation mechanisms of shortcut nitrification, enabled rapid assessment of the feasibility and stability of NO₂⁻-N accumulation, and offered new ideas and methods for process control and real-time monitoring in short-cut nitrification systems.