Abstract: The partial denitrification (PD) process reduces \rmNO_3^- -N and produces \rmNO_2^- -N, which serves as a substrate for anaerobic ammonia oxidation. However, the PD process is highly susceptible to water quality fluctuations and exhibits instability in actual operation. An anoxic sequencing batch activated sludge reactor was developed and optimized to domesticate partial-denitrification denitrifying bacteria, enhancing the shock load resistance of PD process. Batch experiments were conducted to determine the most efficient domestication conditions, specifically the C/N ratio and reaction time. The results indicated: (1) The PD process achieved the maximum efficiency at a C/N ratio of 2.5 and a reaction time of 60 minutes, with a \rmNO_2^- -N conversion efficiency of 70.7%. (2) The C/N ratio was the primary factor influencing the \rmNO_2^- -N conversion rate during PD system operation. Providing a higher C/N ratio (C/N=4) during the reactor's startup phase, gradually reducing it to 2.5 during operation, and increasing nitrogen loading by raising the \rmNO_3^- -N concentration and maintaining a reaction time of 60 minutes facilitated efficient \rmNO_2^- -N accumulation. (3) After 48 days of reactor operation, the abundance of EPS-secreting Terrimonas spp., and denitrifying bacterial genera Ferruginibacter and Ottowia, increased significantly, along with a notable rise in Thauera spp abundance, which was associated with PD. Based on these findings, a regulatory model for the coupled PD and anaerobic ammonia oxidation (PD-A) process was proposed for engineering applications. This model integrates the domesticated partial-denitrification denitrifying bacterial system with the anaerobic ammonia oxidation process, ensuring a stable and efficient supply of \rmNO_2^- -N substrate for anaerobic ammonia oxidation.