Evaluation　on　nitrogen　removal　of　step-feed　anoxic/oxic　activated　sludge　process　at　the　standpoint　of　reaction　kinetics　and　process　kinetics　was　conducted.　Theoretical　biological　nitrogen　removal　efficiency　was　deduced　based　on　the　mass　balance　of　nitrate　in　the　last　stage.　The　comparison　of　pre-denitrification　process　and　step　feed　process　in　the　aspects　of　nitrogen　removal　efficiency,　volume　of　reactor　and　building　investment　was　studied,　and　the　results　indicated　that　step-feed　anoxic/oxic　activated　sludge　process　was　superior　to　pre-denitrification　process　in　these　aspects.