Microbe drives biogeochemical cycling of elements on Earth. Being the fourth most abundant element on earth and the most frequently utilized transition metal in the biosphere, iron (Fe) naturally undergoes active reactions between ferrous and ferric states in circumneutral-pH or acid environment. Due to instability of dissolved Fe(Ⅱ) and adsorptive capability of insoluble Fe(Ⅲ) compounds, active Fe cycling exerts a strong influence on soil geochemistry. Advances in geo-microbiology have transformed our understanding of the edaphic iron cycling from mere physico-chemical reaction to biogeochemical process over the past three decades. Fe ion, undergoing active oxidation-reduction reactions in all life forms, is required asan integral component in cellular processes. And it has been demonstrated that phylogenetically diverse groups of microbes can grow either aerobically or anaerobically using Fe as electron donor or electron acceptor to generate energy from Fe reduction and Fe oxidation in vitro or in vivo. In recent years, significant progresses have been made toward understanding the biochemical mechanisms of microorganisms catalyzing anaerobic reduction of Fe(Ⅲ) in the circumneutral pH environment. Shewanella and Geobacter are the two model organisms commonly used in studyingmechanisms of Fe-reduction, and the use of insoluble ferric oxyhydroxide minerals as terminal electron acceptors in anaerobic respiration through extracellular electron transfer (dissimilatory Fe(Ⅲ) reduction). Comparatively little information is available on mechanisms of Fe(Ⅱ) oxidation at neutral pH conditions. Microaerobic Fe(Ⅱ)-oxidizers, such as Gallionella andLeptothrix, active at circumneutral pH, could compete with O2 in abiotic oxidation of Fe(Ⅱ), forming Fe(Ⅲ) oxide encrustation specific to the oxic-anoxic interface of soil. Fe-oxidizing microbes are not limited to aerobic habitats, but can also oxidize iron under anaerobicconditions using NO3−[nitrate-dependent Fe(Ⅱ)oxidation], or CO2[phototrophic Fe(Ⅱ)oxidation] as the terminal electron acceptor. The microbial Fe(Ⅱ)-Fe(Ⅲ) wheel promotesvarious environmental or ecosystem processes, such as nutrient cycling and contaminant transformation, at the water-soil interphase. It is worthwhile to note that in anaerobic environments, microbial Fe(Ⅲ) reduction is an important pathwayof anaerobic degradation of organic matter. Besides, dissimilatory Fe(Ⅲ) reduction is a key process governing reduction of humic substances, reductive dechlorination and metals reduction. Furthermore, Fe(Ⅲ)-reducing bacteria successfully outcompetemethanogenenic bacteria for H₂ as an energy source, which results in dropping of methane production in soil of high organic matter content. Fe(Ⅱ)-oxidizing microbes have been demonstrated to oxidize both soluble and insoluble Fe(Ⅱ), producing a variety of insoluble Fe(Ⅲ) mineral products. Owing to their high affinity on surface, bacteriogenic iron oxides are ameliorating agents and geochemical barriers for fixing heavy elements, thus generating a major influence on release, transport, immobilization and bioavailability of heavy metals in soil. As a whole, it is apparent that iron biogeochemical cyclingistightly linked to organic matter degradation, denitrification, methane production and metal immobilization, which is one of the most important issues in environmental science.The processes driving iron cycling are not instantaneous, and Fe(Ⅲ) reduction and Fe(Ⅱ) oxidation occur simultaneously in adjacent (micro-scale) locations. Dissimilatory iron-reducing bacteria are found capable of excreting Fe(Ⅲ), resulting in anaerobic reduction of iron oxides in soil. Fe(Ⅱ) species in soils is usually soluble and highly mobile, and able to act as an electron donor for iron oxidizing bacteria. Thus, it is re-oxidized to Fe(Ⅲ), forming secondary iron minerals. So far, it is less understood that the key factors which control Fe-cyclingatcircumneutral pH include local gradients of oxygen, light, nitrate and ferrous iron. And recent researches have demonstrated that environmental organic matter, such as lactate, plays an important role in the transition of Fe(Ⅲ) reduction and Fe(Ⅱ) oxidation. To sum up, in the paper, the authors highlight the process, mechanism and environmental significance of microbe-mediated iron biogeochemical cycling, particularly in circumneutral pH environment that prevailsin soil, and also demonstrate the coupling relationship between iron and other related elements in biogeochemical cycling. Furthermore, the authors discussed key factors controlling shift between Fe(Ⅱ) oxidation and Fe(Ⅲ) reduction. In the end, the authors present their outlook about priority direction of the research on biogeochemical cycling of Fe in soil environment.This review is believed to be conducive to understanding of iron biogeochemical processes in the environment and formation of new strategies for sustainable rational utilization of the soil resources in China.