Uranium contamination is getting more and more attention due to its potential harm to environment and human health. Physical and chemical techniques are widely used in remediation, whereas generally expensive and challenging. Microbial mediated uranium bioreduction is an environmental-friendly technology, showing great potential in uranium remediation. Over the past twenty years, a diverse range of soil bacteria have been identified with the ability in reducing U(VI) to U(IV), including but not limited to Fe(III)-and sulphate-reducing bacteria. The recent progress in molecular mechanisms of bacterial U(VI) reduction was reviewed, especially the various pathways of extracellular electron transfer, including the metal-reducing pathway of Shewanella oneidensis MR-1, the porin-cytochrome-mediated pathway and nanowire pathway of Geobacter sulfurreducens PCA. Competitive electron acceptors and coexisting ions played important roles in bacterial U(VI) reduction. The molecular mechanisms by which bacteria transfer electrons across the outer membrane and then exchange electrons with extracellular minerals remain unclear. It also remains unclear how Geobacter spp. nanowires interact with the porin-cytochrome to transfer extracellular electron. In the future, studies could be focused on the mechanisms of bacterial U(VI) reduction and how to improve the efficiency and stability of uranium bioremediation.