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This paper described an experimental study for treating salt containing wastewater with a bench-scale SBBR (sequencing batch biofilm reactor). By gradually increasing salinity of the wastewater, the activated sludge of high salt-tolerance was acclimatized, and the treatment test of simulated salt wastewater was carried out with wastewater samples of five sorts of salinity: 0 g/L, 8 g/L, 16 g/L, 24 g/L and 32 g/L. The experimental results showed that with the increase of salinity gradient, the efficiencies of removing NH4+-N, COD and TP decreased notably: in case where salinity was 32 g/L, and compared with salinity of 0 g/L, NH4+-N declined from 98% to 84%; COD from 98% to 73%; and TP from 97% to 47%. Additionally, the microbial activity, which was characterized by SOUR (specific consumption rate) and DHA (dehydrogenase activity) of biofilm, increased on condition of salinity being below 8 g/L, while decreased when salinity was up to greater than 8 g/L. Salinity made it possible to increase the content of extracellular polymer (EPS) in biofilms from 26.15 mg/g SS to 216.27 mg/g SS, among which polysaccharide (PS) content of TB-EPS grew most, and the increase of EPS could improve the resistance of microorganisms to salinity and the cells' protective effectiveness. It was found that under different salinity conditions there were growing three largest dominant phyla: actinomycetes, proteomycetes and patella bacteria in the biofilms, and the average relative abundance remained between 72% and 83%, among which the relative abundance of actinomycetes increased significantly with the increase of salinity, and the relative abundance of variant phylum decreased with the increase of salinity; the relative abundance of Kineosphaera, Micropruina and TM7a increased rapidly with the increase of salinity, and on the condition of salinity being up to 32 g/L, they became the three biggest dominant genera. To sum up, from the perspective of microbial community characteristics, the effects of increasing salinity on the structure and diversity of microbial communities were explored, the results could provide a theoretical basis for the further study on COD, NH4+-N and TP removal mechanisms of SBBR systems under high salinity stress. [ABSTRACT FROM AUTHOR]