Abstract: 10 strains,capable of degrading and decolorizing bromamine acid under high salt conditions,which is an intermediate of anthraquinone dye,were isolated from the biomembrane of a bio-contact oxidation tank.A strain named C-7 which has good decolorizing effect and stable decolorization ability was obtained by acclimating the 10 strains.It was identified as Citrobacter freundil.Salt tolerance test results show that the strain C-7 can grow with a decolorization rate of more than 80% when the mass fraction of NaCl is 1% to 3%,and NaCl has no effect on the growth and decolorization of the strain.When the mass fraction of NaCl is 7%,C-7 show high tolerance and the decolorization rate is more than 50%.NaCl can inhibit the growth of the strain C-7 and bromamine acid cannot be degraded when the mass fraction increases to 10%.Under the optional growth conditions of pH 7.0,the rotating rate of 160r·min^-1,the liquid volume of 120mL in a 250mL flask,inocula of 10% and peptone of 7g·L^-1 as the only nitrogen source,when the mass fraction of NaCl is 1%,the decolorization rate of bromamine acid(100mg·L^-1) can reach to 85% or higher.