Hydroxylamine　(NH2OH)　and　hydrazine　(N2H4)　are　crucial　intermediates　in　biological　nitrogen　removal　processes,　but　their　potential　effects　on　the　nitrogen-related　metabolic　pathway　during　the　sulfur-driven　autotrophic　denitrification　(SDAD)　process　remain　unclear　and　were　thus　explored　in　this　work.　The　results　of　dedicated　batch　tests　indicated　that　the　accumulation　ratio　of　NO2-　was　positively　correlated　with　the　NH2OH　concentration,　reaching　86.2　+/-　2.6%　at　the　NH2OH　concentration　of　2.0　mg-N/L,　while　it　was　barely　affected　by　the　N2H4　concentration.　Furthermore,　the　joint　inhibition　of　NH2OH　and　free　nitrous　acid　led　to　the　substantial　accumulation　of　N2O　(up　to　32.9　+/-　1.3%)　during　the　NO2-　reduction　phase.　In　contrast,　N2H4　exhibited　great　potential　for　facilitating　N2O　accumulation　in　both　the　NO3-　reduction　and　NO2-　reduction　phases　with　an　accumulation　ratio　of　13.0　+/-　0.3%　and　27.5　+/-　1.5%,　respectively,　at　the　N2H4　concentration　of　2.0　mg-N/L.　Total　enzyme　activity　analyses　revealed　that　the　presence　of　NH2OH　inhibited　the　activity　expression　of　all　denitrifying　enzymes,　with　the　downstream　enzymes　(such　as　NO2-　reductase　and　N2O　reductase)　being　more　susceptible　to　NH2OH.　The　addition　of　N2H4　did　not　cause　a　significant　decrease　in　the　activity　of　NO3-　reductase　and　NO2-　reductase,　but　notably　curbed　the　activity　of　N2O　reductase.　Based　on　the　responses　of　the　SDAD-related　nitrogen　metabolic　pathway　to　NH2OH/N2H4,　this　work　provided　effective　technical　means　for　i)　the　promotion　of　NO2-　accumulation　which　might　enable　the　coupling　of　SDAD　with　Anammox　and　ii)　the　efficient　recovery　of　N2O　via　the　SDAD　process.