A novel electrochemical strategy for economical, environmental-friendly, simple and facile synthesis of glycine functionalized graphene quantum dots (GQDs) based on direct exfoliation and oxidation from graphite rods was reported. The average diameter of as-synthesized GQDs is 30 nm. Due to the rich nitrogen and oxygen functional groups on the surface of GQDs, the GQDs dispersion was bright yellow and further applied in selective detection of ferric ion (Fe 3+ ). A sensor based on photoluminescence quenching of GQDs after adding Fe 3+ has a limit of detection of 3.09 μM, which is lower than the maximum level (0.3 mg/L, equivalent to 5.4 µM) of Fe 3+ permitted in drinking water by the U.S. Environmental Protection Agency (EPA). The fluorescent sensor has a wide linear range of 10–150 μM. Moreover, due to the low cytotoxicity of as-prepared GQDs, this study may provide a new analytical platform for further applications of GQDs in real environmental and biological system.