Variation　of　dissolved　organic　matters　(DOM)　in　mainstream　anammox　process　has　received　limited　attention.　This　study　systematically　characterized　DOM　and　dissolved　organic　nitrogen　(DON)　in　a　full-scale　mainstream　anammox　wastewater　treatment　plant　(WWTP)　using　spectroscopy　and　Fourier　transform-ion　cyclotron　resonance　mass　spectrometry.　Roles　of　bacterial　community　structures　related　with　temperatures　on　DOM　and　DON　transformations　were　analyzed.　Results　indicated　that　the　WWTP　removed　highly　bioavailable,　S-containing　DOM　while　producing　more　unsaturated,　aromatic,　and　N-containing　DOM.　Higher　relative　abundances　of　Proteobacteria　and　Chloroflexi　at　low　temperature　resulted　in　greater　removal　rates　of　proteins,　SMP-like　and　humic　acid-like　substances.　At　high　temperature,　higher　relative　abundance　of　Actinobacteriota　increased　lignin　production.　Principal　component　analysis　revealed　that　temperature　significantly　impacted　DOM　characteristics　compared　to　DON.　These　findings　are　crucial　for　understanding　DOM　and　DON　transformation　during　mainstream　anammox　WWTP.