Abstract: It was studied that treating domestic saline wastewater in sequencing batch reactors,different salinity's affection on the specific nitrification,denitrification rate and domin community in the activated sludge system.The experiment utilized three parallel SBR reactors,the ratio of influent,aerobic,anoxia, sedimentation and effluent time was 0.17 h,7 h,3 h,1.5 h and 0.33 h,the three SBR systems' salinity were 5,7.5,10 g/L,respectively.The three systems were operated for 50 days in a steady state.The results showed that:NaCl salinity had higher inhabitation to nitrobacteria than to denitrifier,NaCl salinity had higher inhabitation to NOB than to AOB,7.5 g/L and 10 g/L systems performed short-term nitrification-denitrification in a short time.Nitrite accumulation rate could be maintained above 95%.With the raising of salinity,specific nitrification rate of three systems declined in a steady state.5 g/L and 7.5 g/L systems' had higher ammonia removal rate in a steady state.Salinity of 7.5 g/L was a perfect salinity which could result in short-term nitrification-denitrification in an activated sludge system.