Abstract：Iron-based composites exhibit superior performance for adsorption/immobilization of heavy metals and are thus frequently used for passivating Pb in soil. However， the common method for their synthesis is of high cost. Herein， we propose the preparation of iron-based Pb-immobilized materials based on the utilization of iron sludge （IS） generated from Fenton process. Dissimilatory iron reduction of IS by Shewanella Oneidensis MR-1 was performed to generate the vivianite/bacteria （Vivi/MR-1） composites with abundant functional groups， large surface area， and high amounts of negative surface charge. It was revealed that the maximum adsorption capacity of Vivi/MR-1 for Pb was 118 mg·g-1， which was significantly higher than that of MR-1 （78 mg·g-1）， IS （61 mg·g-1）， and Vivi （52 mg·g-1）. The Vivi/MR-1 for Pb adsorption worked efficiently in a wide pH range and slightly affected by the presence of other metal ions. The results of X-ray diffractometer （XRD） and Fourier Transform Infrared Spectrometer （FTIR） confirmed that adsorption mineralization and functional group complexation are the dominant mechanisms for Pb immobilization. Further experiments with the contaminated soil verified that the as-synthesized Vivi/MR-1 was effective in immobilizing Pb， with a substantial decrease （by 93.6%） in the acid-soluble Pb in the soil.