In　this　research,　NO3--N　was　added　into　the　typical　sludge　anaerobic　fermentation　(TAF)　of　waste　activated　sludge　(WAS),　creating　an　anoxic　environment　for　the　growth　of　denitrifiers,　as　well　as　the　inhibition　of　methanogens,　therefore　to　insure　the　operation　of　simultaneous　anoxic　fermentation　and　denitrification　(SAFD)　system.　Compared　to　TAF,　SAFD　can　utilize　the　endogenous　carbon　source　of　WAS　to　denitrification,　which　achieved　higher　sludge　reduction.　Results　showed　that　the　SS,　VSS　in　SAFD　was　reduced　by　63.8%　and　74.7%,　respectively,　which　is　obviously　higher　than　that　of　36.7%　and　47.6%　in　TAF.　Volatile　fatty　acids　(VFAs)　in　TAF　reached　the　top　with　propionic　acid　as　dominant　component　in　the　mid-period　of　the　fermentation;　whereas　that　in　SAFD　was　preferred　by　acetic　acid　in　the　late　period.　Evidenced　by　the　variation　of　TN,　NH4+-N　and　NO3--N,　SAFD　own　a　significant　ability　in　denitrification,　while　the　protein　conversion　appeared　to　be　continuously　low　in　this　system.