Redox potential (E h ) is an index used to assess the oxidation and reduction conditions in the environment. Since heavy metals (HMs) easily react with E h -sensitive substances by adsorption, complexation and precipitation etc., E h fluctuation has a significant impact on the toxicity and lability of HMs. Researches have showed that the changes of E h have a bidirectional effect on heavy metal lability: firstly, E h declines in flooded environments, triggering denitrification and reduction of iron and manganese oxides and sulfides, and pH tends to be neutral, which indirectly leads to the precipitation of exchangeable HMs in acidic soils or the release of adsorbed HMs in alkaline soils; secondly, alteration in the form and content of iron and manganese oxides, organic matter and sulfides can result from the change of E h . In anoxic environments, HM solubility maybe enhanced by the reduction of iron and manganese oxides and the decomposition of organic matter into dissolved organic matter which can complex HM ions. In contrast, the HM ions may also precipitate out as metal sulfides and be reduced to less toxic species such as Cr, Hg etc.; In oxic conditions, HMs in metal sulfides can be oxidized into sulfates, but they can also be adsorbed onto amorphous Fe/Mn oxides, formed by Fe, Mn precipitation or alteration in oxides, as free metal ions. These complex chemical reactions make it more difficult to quantify the impact of E h on HM behavior, thus reducing the accuracy of the risk assessment of HMs in an E h fluctuation environment (paddy soil, cyclical tidal flat sediments, etc.). This also limits the implementation of in situ remediation procedures by changing E h for HM-contaminated soil. Therefore, it is necessary to carry out further research on HM-related reactions induced by E h change on soil surfaces and develop analytical techniques, such as non-destructive physical detection methods or isotope dilution techniques, to establish quantitative relationships between E h and HMs speciation and lability in different soils, so that the mechanism of the effect of E h on heavy metal speciation can be revealed. © 2018, Editorial Board, Research of Environmental Sciences. All right reserved.