Measurement　and　predicted　variations　of　ammonia　oxidation　rate　(AOR)　are　critical　for　the　optimization　of　biological　nitrogen　removal,　however,　it　is　difficult　to　predict　accurate　AOR　based　on　current　models.　In　this　study,　a　modified　model　was　developed　to　predict　AOR　based　on　laboratory-scale　tests　and　verified　through　pilot-scale　tests.　In　biological　nitrogen　removal　reactors,　the　specific　ammonia　oxidation　rate　(SAOR)　was　affected　by　both　mixed　liquor　volatile　suspended　solids　(MLVSS)　concentration　and　temperature.　When　MLVSS　increased　1.6,　4.2,　and　7.1-fold　(1.3-8.9　g/L,　at　20　degrees　C),　the　measured　SAOR　decreased　by　21%,　49%,　and　56%,　respectively.　Thereby,　the　estimated　SAOR　was　suggested　to　modify　when　MLVSS　changed　through　a　power　equation　fitting.　In　addition,　temperature　coefficient　(theta)　was　modified　based　on　MLVSS　concentration.　These　results　suggested　that　the　prediction　of　variations　ammonia　oxidation　rate　in　real　wastewater　treatment　system　could　be　more　accurate　when　considering　the　effect　of　MLVSS　variations　on　SAOR.