Influences of various concentrations of salinity (NaCl 0-25.0 g/L) on partial nitritation performance in a zeolite biological aerated filter (ZBAF) were investigated. The highest nitrite production rate (NPR) of 1.357 kg/(m(3).d) and nitrite accumulation rate (NAR) of 99.0% was achieved with salt free wastewater. While after adding extra salt, NPR and ammonium removal efficiency (ARE) presented an obvious decline trend. The lowest NPR (0.599 kg/(m(3).d)) and ARE (34.2%) were obtained with salinity of 25.0 g/L NaCl. It has been confirmed that addition of salt resulted in the increase of free ammonia (FA), and then further inhibited ammonium oxidizing bacteria (AOB). High-throughput sequencing analysis results further revealed that the relative abundance of AOB decreased in ZBAF. All results demonstrated that AOB was inhibited not only by high osmotic pressure caused by salt, but also by high FA.