Tetrabromobisphenol-A (TBBPA) was widely used in electronic equipments,plastics,textiles and many other applications duo to its good flame retardants.TBBPA has primarily been detecteded in air,soil,water,sewage sludge,or sediment,and showed high toxicity to aquatic animals and humans.It was demonstrated that TBBPA could reduced by anaerobic sludge,but little is known about its environmental fate and process mechanism.Here we investigated the effects of humic acid on biodegradation of TBBPA.The results showed that many kinds of humic acids could accelerate the anaerobic biodegradation of TBBPA.After 72 h,approximately 44% of TBBPA (initial concentration of 80 mg/L) was removed from the medium in cultures of Shewanella sp.with 90 mg L-1 humic acids extracted from activated sludge and 20 mM sodium lactate as electron donor.No evidence of TBBPA reduction were achieved without humic acids and better results were observed with higher humic acids concentration.It was also found that the humic acids could improve TBBPA solubility in water and have redox activities,which could act as electron shuttles for accelerating TBBPA biotransformation.