Under anaerobic conditions, the characteristics of sulfate reducing bacteria (SRB) were applied to reduce U(VI) under different temperature, pH values, U(VI) concentrations and coexisting ions. The results showed that the optimum reduction condition was the temperature 35 degrees C, pH 7.0 and U(VI) concentration 25 mg x L(-1). The maximum reduction capacity of SRB was 179.1 mg x g(-1). Mo(VI) or Ca2+ did not affect SRB on the reduction process of U(VI) under the concentration less than 5 g x L(-1), but they strongly inhibited the process under the concentration more than 20 g x L(-1). The main inhibition of Mo (VI) was physiological inhibition and the inhibition of Ca2+ was competitive inhibition through the stable complex formation, Ca-UO2-CO3. The results also showed that lag phase did not appear on the concentration of Ca2+ less than 5 g x L(-1), but the lag phase of 24 hours appeared on the concentration of Ca2+ more than 20 g x L(-1).