Abstract: Graphene-based nanomaterials are attractive as high performance sensors owing to their unique properties, such as high specific surface area, high electron mobility, and exceptionally low electronic noise. Graphene/graphene oxide (GO)-based nanomaterials are promising and are being developed for the rapid detection of environmental and health-threatening heavy-metal ions with a high sensitivity. Recent advances in the electrochemical detection of heavy-metal ions using graphene or GO are reviewed. Sensors based on graphene composites have high sensitivities and detection limits below 1 nM for Cd(Ⅱ), Pb(Ⅱ), Cu(Ⅱ) and Hg(Ⅱ), which are lower than the allowable concentrations of these ions in the human body as set by the World Heath Organization.