Acrylic　fiber　(AF)　wastewater　is　characterized　by　high　levels　of　ammonia　nitrogen,　refractory　organic　compounds,　and　toxic　substances,　making　biological　nutrient　removal　challenging.　Conventional　biological　treatment　technologies　are　often　ineffective　due　to　the　complex　composition,　high　toxicity,　and　low　C/N　ratios　of　AF　wastewater.　In　this　study,　a　two-stage　nitrification-partial　denitrification/anammox　(N-PDA)　process　was　firstly　developed　for　the　combined　treatment　of　AF　wastewater　and　domestic　sewage,　which　integrated　nitrificationSBR(N-SBR)　and　partial　denitrification/anammox-UASB　(PDA-UASB).　The　N-SBR　achieved　stable　nitrification　(ARE=100　%,　HRT=4.2　h)　with　increasing　ratios　of　AF　wastewater,　while　the　PDA-UASB　utilized　organic　carbon　from　domestic　sewage　to　simultaneously　remove　nitrate　(91.7　mg/L)　and　ammonium　(66.3　mg/L)　through　the　PDA　pathway　(HRT=11.3　h).　After　200　days,　the　relative　abundance　of　Candidatus　Brocadia　increased　from　0.6　to　5.4　%,　ensuring　robust　nitrogen　removal　performance.　The　system　achieved　effluent　ammonium　and　total　nitrogen　concentrations　below　1.0　mg/L　and　15.0　mg/L,　respectively,　with　a　total　nitrogen　removal　rate　of　87　%.　This　study　demonstrates　the　N-PDA　process　as　an　efficient,　energy-saving,　and　cost-effective　solution　for　treating　AF　wastewater　without　the　additional　organic　carbon　sources,　enhancing　nitrogen　removal　efficiency　and　operational　stability.