This　study　presents　an　innovative　mainstream　Anammox　based　on　multiple　NO2--N　supplement　pathways　to　treat　actual　mature　landfill　leachate　over　180　days.　Desirable　effluent　quality　of　11.8　mg/L　total　nitrogen　(TN)　and　nitrogen　removal　efficiency　of　98.8%　were　achieved　despite　fluctuation　conditions　of　1.5-fold　influent　substrates　and　8.0-fold　dissolved　oxygen　overload.　Nitrogen　mass　balance　confirmed　Anammox　was　the　dominant　nitrogen　removal　pathway,　contributing　up　to　87.9%.　Functional　genes　of　ammonia　monooxygenase　(amoA),　hydrazine　synthase　(hzsB),　and　ratio　of　nitrate/nitrite　reductase　were　highly　detected.　Anammox　genera,　Candidatus_Kuenenia　(4.1%)　and　Candidatus_Brocadia　(5.3%)　were　dominant　in　two　functional　systems,　respectively,　due　to　the　different　affinity　of　nitrite,　oxygen,　and　organic　carbon.　As　an　economical　and　sustainable　technology,　the　innovative　process　enabled　a　95.1%　decrease　in　organic　carbon　demand,　a　61.5%　reduction　in　aeration　energy　consumption,　and　77.6%　lower　biomass　production　compared　with　traditional　nitrification-denitrification　process.