Abstract: The effect of NaCl salinity,hydraulic retention time,and influent loading on short-cut nitrification and denitrification was investigated using sequencing batch reactor.Results show that the accumulation rate of NO₂^--N is higher than 50% when NaCl salinity,pH,temperature,dissolved oxygen,influent chemical oxygen demand and concentration of ammonia nitrogen are 5.8-25.0 g/L,7.5-8.5,30-35 ℃,0.5-1 mg/L,450-550 mg/L,and 35-45 mg/L,respectively.Furthermore,nitrite accumulation rate is higher than 99% when NaCl salinity,HRT,organic loading and ammonia nitrogen loading daily of 1 kg suspended solids contained are 14.5 g/L,6.21 h,5.03×10^-2 kg and 2.24×10^-3 kg,respectively.Therefore,shortcut nitrification and denitrification can be achieved by controlling HRT,organic loading and ammonia nitrogen loading at high concentration of NaCl.The limiting concentration of NaCl for nitrosobacteria is up to 25 g/L.