In　order　to　improve　removal　efficiency　of　nitrogen,　to　enhance　nitrogen　removal　process　for　low　C/N　ratio　wastewater,　and　to　accomplish　denitrification,　primary　sludge　was　used　as　carbon　source　and　NOx--N　was　added　into　primary　fermentation　system(PF)in　this　study.　By　investigating　the　variation　of　VFAs(volatile　fatty　acids)accumulation,　NOx--N　removal　amount　and　VSS(volatile　suspended　solids)reduction,　the　fermentation　and　denitrification　capacity　of　4　different　electron　acceptor　systems　were　contrasted.　The　results　showed　that　VFAs　had　little　accumulated　for　sole　NO3--N　and　combined　of　NO2--N　and　NO3--N　systems,　while　for　sole　NO2--N　and　anaerobic　systems　VFAs　showed　great　accumulation,　indicating　that　the　use　of　carbon　source　was　better　for　NO3--N　and　combined　system.　The　total　amount　of　removing　electron　acceptor　for　sole　NO3--N,　combined　NO2--N　and　NO3--N　and　sole　NO2--N　systems　were　1692　mg·L-1,　1330　mg·L-1,　1223　mg·L-1,　respectively.　Clearly　sole　NO3--N　system　had　the　best　denitrification　ability.　Additionally,　all　these　electron　acceptor　systems,　with　more　than　60%　VSS　reduction,　showed　a　great　sludge　reduction　capacity,　especially　for　NO3--N　system,　which　reached　about　67.9%,　even　though　little　decreased　compared　to　the　anaerobic　system.　In　summary,　for　primary　fermentation　and　denitrification　system,　using　NO3--N　as　electron　acceptor　can　achieve　the　best　nitrogen　removal　efficiency　and　sludge　reduction　performance.　©　All　Rights　Reserved.