The innovative DEnitrifying AMmonium OXidation (DEAMOX) process, coupling partial-denitrification (PD) with anammox, was designed for treating high-strength nitrate (NO3--N) and ammonia (NH4+-N) wastewater for the first time. With influent total nitrogen (TN) up to 1600 mg L-1 (NO3--N/NH4+-N of 1.0), DEAMOX process proved to be relatively stable for simultaneously removing NO3--N and NH4+-N. The step-feeding organic carbon (OC) demonstrated as an efficient strategy for avoiding NO2--N consumption by denitrification, facilitating the increased of NO3--N to NO2--N transformation ratio (NTR) to 99% at COD/NO3--N of 1.77. The TN removal was significantly enhanced to 96.7% with the considerably high anammox contribution of 88.9%. Also, the inhibitory effect of high NO2--N accumulation on denitrifying bacteria could be mitigated. High-throughput sequencing revealed a relatively stable cooperation of functional groups in DEAMOX system. Genus Thauera possibly capable of NO2--N accumulation remained dominant (39.81% to 44.09%), while Candidatus Brocadia responsible for anammox was detected with much lower percentage (2.01% to 1.81%). Results of qPCR confirmed the evident growth of anammox bacteria under increasing nitrogen and organic loading. The DEAMOX process offers a significantly stable and efficient method in treating high-strength NO3--N and NH4+-N wastewater.