To promote efficiency nitrogen-rich wastewater treatment from a sequencing batch biofilm reactor (SBBR), three aerobic denitrifiers (Pseudomonas mendocina IHB602, Methylobacterium gregans DC-1 and Pseudomonas stutzeri IHB618) with dual-capacities of strong auto-aggregation and high nitrogen removal efficiency were studied. The aggregation index analysis indicated that coaggregation of the three strains co-existed was better when compared with one or two strains grown alone. Optimal coaggregation strains were used to bioaugmente a test reactor (SBBRT), which exhibited a shorter time for biofilm-formation than uninoculated control reactor (SBBRC). With different influent ammonia-N loads (150, 200 and 300 mgL-1), the average ammonia-N and nitrate-N removal efficiency were all higher than that in SBBRC, as well as a lower nitrite-N accumulation. Microbial community structure analysis revealed coaggregation strains may successfully colonize in the bioreactor and be very tolerant of high nitrogen concentrations, and contribute to the high efficiency of inorganic nitrogen-removal and biofilm-formation.