It　was　realized　nitrite　accumulation　in　a　pilot-scale　pre-denitrification　process　at　normal　temperature.　The　influence　factors,　temperature,　pH,　FA　and　DO,　for　nitrite　accumulation　were　analyzed.　The　nitrite　was　accumulated　in　the　beginning　time　with　the　DO　kept　at　0.5　mg/L,　however　the　phenomenon　of　nitrite　accumulation　was　vanished　when　the　DO　increased　to　1.5　mg/L.　At　last　the　nitrite　accumulation　was　resumed　when　DO　reduced　to　0.5　mg/L.　So　it　could　be　obtained　that　DO　was　the　main　factor　to　realize　nitrite　accumulation　in　the　study.　It　was　found　that　it　was　possible　to　keep　stable　and　high　nitrite　accumulation　effectively　control　DO　at　0.5　mg/L.