In　order　to　investigate　the　variations　of　specific　oxygen　uptake　rate　(RSOUR)　and　its　feasibility　during　nitrification　as　a　control　parameter　in　activated　sludge　system,　a　method　was　presented　realizing　on-line　determination　and　feedback　in　SBR　process.　Two　SBRs　were　seeded　with　activated　sludge　of　nitrite-oxidizing　bacteria　(NOB)　and　nitrite-oxidizing　bacteria　(AOB)　as　the　dominant　bacteria,　respectively.　The　variations　of　SOUR　under　constant　dissolved　oxygen　concentration　were　studied　and　results　showed　RSOUR　of　SBR1　decreased　dramatically　from　0.01　to　0.004　mg　O2　per　gram　and　minute,　after　290　min　aerobic　reaction　time,　while　that　of　SBR2　declined　from　0.074　to　0.013　mg　O2　per　gram　and　minute,　after　206　min　aerobic　reaction　time　at　the　completion　of　ammonium　oxidation.　The　sharp　decline　of　RSOUR　indicated　the　completion　of　nitrification,　then　aeration　should　be　terminated.　RSOUR　curve　can　exactly　reflect　the　process　of　nitrification,　all　of　which　may　well　lay　a　theoretical　foundation　for　application　of　SOUR　as　on-line　control　parameters.