Abstract: The bioremediation behavior and mechanism of sulfate reducing bacteria (SRB) granular sludge which was artificially domesticated were studied. U(Ⅵ) removal by SRB granular sludge was investigated under micro-aerobic condition with the concentration of oxygen 0.6-1.0 mg/L, then the removal mechanism was analyzed with FTIR, SEM and EDS, and finally the deposit morphology of uranium was studied with the sequential extraction procedure. The results show that U(Ⅵ) removal by SRB granular sludge mainly occurs following a 2-step process which is initial adsorption(the first 30 min) and microbial reduction process. The ultimate removal rate of U(Ⅵ) reaches 98.89%. Analyses of FTIR, SEM and EDS indicate that groups-amide group, carboxyl, hydroxyl and phosphoric acid group coming from the surface of SRB granular sludge are involved in uranium deposition. Ion exchange happens between Na⁺ or Mg²⁺ and UO²⁺₂. Finally, U(Ⅵ) mainly deposites on granular sludge in the form of residual state that has poor bioavailability, bad migratory aptitude and less secondary pollution.