Abstract: To study the properties and effect factors of endogenous denitrification via nitrite, an SBR reactor was operated in denitrification at 20 C using nitrogenous electron acceptor, i.e. NO₃^- and NO₂^-. Moreover, the endogenous partial denitrification rate was investigated at different mixed liquor suspended solids (MISS). The results show that endogenous denitrification rate via nitrite was 1.6 times as much as that via nitrate. When the mixed liquor suspended solids changed from 4 g/L to 12 g/L, the endogenous denitrification rate increased from 0.026d^-1 to 0.038d^-1. After 9 cyles of batch operation, a volatile suspended solids (VSS) reduction of 16% was achieved with a denitrification rate decrement of 49%.