It is not successful to denitrify waste-water with high content of salt by freshwater activated sludge because of salinity choking.To overcome this problem，halophilic activated sludge must be developed.In this study，activated sediment at estuary of a river was collected and cultured to get halophilic activated sludge.The effect of key factors，such as salinity，temperature，pH and carbon source etc.，on denitrifying-nitrite performance of the halophilic activated sludge was studied.The results show that nitrite can be denitrified by the halophilic system via utilizing it as electron acceptor.As a result，the halophilic activated sludge is of ability to denitrify highly saline wastewater.At 38 g·L-1 salinity environment，the maximum specific denitrification rate of the biological system is 3.29 mg N·（g VSS）-1·h-1.These key operation parameters were optimized for further engineering design：the optimal survival salinity is 15—51 g·L-1 and pH 8.0—9.0.Carbon source has a great influence on denitrification rate.Among methanol，acetate，propionic and glucose tested，methanol is the best because it is beneficial electron donors. As a new different biological system，the halophilic activated sludge，it is of important significance for treatment of saline wastewater to establish their characteristic of denitrification and influencing factors.