Phosphorus　release　(P-release)　is　one　of　the　important　factors　in　enhanced　biological　phosphorus　removal　(EBPR)　process,　and　insufficient　P-release　usually　is　the　main　reason　for　the　instability　of　EBPR.　In　order　to　study　the　effect　of　different　types　of　carbon　sources　on　P-release,　the　effluent　activated　sludge　of　the　aerobic　zone　of　the　anaerobic-anoxic-aerobic　oxidation　ditch　process　was　used.　Different　types　of　carbon　sources,　such　as　acetate,　propionate,　glucose,　ethanol　and　methanol　were　used.　The　main　test　was　made　though　captive　test　with　a　10　L　reactor.　The　results　indicated　that;　(1)　In　anaerobic　conditions,　poly　P-accumulating　organisms　(PAOs)　released　P　rapidly　with　acetate　or　propionate　acting　as　carbon　sources,　and　the　specific　P　release　rate　was　290.5　and　236.7　mg　P·(g　VSS)-1·d-1,　respectively.　However　with　glucose,　ethanol　or　methanol　acting　as　carbon　source,　P　released　slowly,　the　specific　P　release　rate　was　49.4,　38.8　and　8.91　mg　P·(g　VSS)-1·d-1　respectively.　(2)　Whereas　in　anoxic　conditions,　P　release　rate　was　just　the　same　as　the　anaerobic　conditions　if　acetate　or　propionate　acted　as　carbon　sources.　But　P　was　seldom　released　with　glucose,　ethanol　or　methanol　acting　as　carbon　source　in　anoxic　conditions.　(3)　PAOs　utilized　NO3-　to　uptake　P　after　P-release,　if　original　NO3-　was　high　enough,　and　acetate　acted　as　carbon　source.