Abstract: The sludge collected from the sea sediment in Bohai was enriched to isolate Fe (Ⅲ)-reducing bacteria.A Fe(Ⅲ)-reducing bacterium, Enterococcus sp.ZQ21 (GenBank MF192756), was isolated using three layer plate method and identified by 16S rRNA gene sequence analysis.The characteristics of Fe(Ⅲ)-reduction by strain ZQ21 was investigated under different conditions.The results showed that strain ZQ21 had the highest Fe(Ⅲ)-reducing activity with Fe(Ⅱ) concentration of 113.14±3.46 mg/L, using pyruvate as electron donor among EDTA-2Na, citrate, glucose, acetate, pyruvate and formate.Fe(Ⅲ)-reducing activity by strain ZQ21 using ferric citrate and iron hydroxide as electron acceptors was not the same, with Fe(Ⅱ) concentration of 91.75±1.45 mg/L, 58.39±4.34 mg/L respectively.Fe(Ⅲ)-reducing activity was improved by the addition of anthraquinone-2-sulfonic acid sodium (AQS) when iron hydroxide was as electron acceptors.At the AQS concentration of 1.50 mmol/L, it had the highest Fe(Ⅱ) concentration of 80.28±3.95 mg/L, which increased Fe(Ⅱ) concentration by 27% compared with that of the control group.The Fe(Ⅲ)-reducing bacterium ZQ21 showed high Fe(Ⅲ)-reducing activity using soluble and insoluble electron acceptors, which will provide the relevant experimental evidence for the application of dissimilatory Fe(Ⅲ)-reducing bacteria for the purification of pollutants in the marine environment.