The　effects　of　acetate　and　propionate　on　biological　nitrogen　and　phosphorus　removal　in　a　plug-flow　A(2)O　process　were　evaluated　in　this　study.　The　wastewater　quality　indexes　and　operation　parameters　were　the　same　when　different　carbon　sources　were　used.　However,　we　observed　no　obvious　effect　of　carbon　source　on　nitrogen　removal.　Denitrifying　phosphorus　removal　was　found　to　play　an　important　role　in　simultaneous　nitrogen　and　phosphorus　removal　in　anoxic　reactors　because　almost　the　entire　carbon　source　was　used　for　polyhydroxyalkanoate　(PHA)　synthesis　in　anaerobic　reactors,　and　there　was　no　external　carbon　source　left　for　heterotrophic　denitrification.　Propionate　was　found　to　be　a　more　effective　and　energy-saving　carbon　source　for　biological　nitrogen　and　phosphorus　removal.　In　addition,　the　variations　in　the　metabolic　chemicals,　such　as　phosphorus,　PHA,　glycogen,　and　oxygen,　were　lower　when　propionate　was　used　than　when　acetate　was　used.