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 NO-3 to uptake P after P-release，if original NO-3 was high enough，and acetate acted as carbon source.