Sludge reduction by electrolysis and its subsequent influence on removal rate of COD, NH3-N, PO43- and on the sludge activity in the aeration tank were investigated. In this research, two parallel sequencing batch reactors were used with one set was operated in convention modality and the sludge of the other set was electrolyzed and then fed back to the reactor. The results showed that: sludge electrolyze could reduce the sludge production around 21% and had slight effect on substrate removal efficiency. After the sludge being electrolyzed, removal rate of COD and NH3-N decreased by 1.1% and 6.9%, respectively. PO43- removal rate increased by 6.1%. The number of protozoa, metazoan and protonema decreased and the structure of sludge floc became more compact. Moreover, the activity of microorganism and carbon source metabolism of sludge changed slightly, but the microbial community structure and metabolic function of microorganism had little change.