Abstract: A simple and economical approach to produce graphene nanosheets (GNSs) in quantity based on the thermal expansion of graphite oxide (GO) powder has been developed, and the as-prepared GNS was further used for the detection of different trace heavy metal ions including Cu²⁺, Pb²⁺, and Cd²⁺. The few-layer GNSs with defects and residual —OH groups were shown to be particularly well suited for the determination of metal ions in the liquid phase using an electrochemical method, in which a remarkably low detection limit of 10^-11mol/L for Pb²⁺ was achieved. The high-yield production technique of GNSs combined with the high sensitivity for the detection of metal ions could promote the development of the industrial manufacture of graphene-based nanosensors.