Sludge　anoxic　dermentation　and　denitrification(SAFD)system　was　established　by　adding　NO3--N　into　the　typical　sludge　anaerobic　fermentation　system.　In　SAFD,　denitrifiers　can　utilize　the　carbon　source　generated　in　waste　activated　sludge(WAS)fermentation　for　denitrification.　This　system　was　aimed　at　dealing　with　the　carbon　source　shortage　and　WAS　treatment　difficulties　in　waste　water　treating　plants(WWTPs).　The　results　indicated　that　suspended　solid(SS)and　volatile　suspended　solid(VSS)decreased　by　63.8%　and　74.7%,　respectively,　presenting　a　remarkable　effect　in　sludge　reduction　when　SRT=60d.　At　the　meantime,　it　showed　a　good　denitrifying　performance　with　complete　removal　of　NO3--N　in　the　early　period　of　the　cycle.　SAFD　could　achieve　simultaneous　fermentation　and　denitrification,　indicating　a　better　performance　than　typical　anaerobic　fermentation.　Investigations　into　the　denitrification　rate　during　the　cycle　demonstrated　that　denitrification　rate　was　higher　in　the　early　period　(the　5th　day),　while　decreased　gradually　and　denitrification　was　accompanied　with　the　accumulation　of　volatile　fatty　acids(VFAs).　Besides,　pH　and　oxidation　reduction　potential(ORP)curves　reflected　the　process　capability　level　of　fermentation　and　denitrification　in　SAFD　system.　Conclusions　of　this　study　could　provide　reference　for　technological　upgrading　of　WWTPs.　©　All　Rights　Reserved.