Using the pure culture technology, we analyzed 26 predominant bacterial strains isolated from a denitrifying quinoline-degrading bioreactor. The capacity of denitrification and aerobic degradation for quinoline of these strains was determined. Then the ability of denitrifying degradation of quinoline by selected denitrifying strains was measured. The results showed that 10 strains of isolates, which belong to Bacillus, Staphylococcus, Pseudomonas, Brucella and Delftia, were denitrifying bacteria. Whereas, 9 strains of isolates belonging to Rhodococcus had the ability of quinoline degradation under aerobic condition. This work described the metabolism function of the major predominant bacteria of microbial community in a quinoline degrading bioreactor. Diverse bacteria, in terms of metabolism, existed in the anoxic denitrifying bioreactor.