An effective technique for production of GQDs by cutting of the GO sheets was developed and the application for detection of heavy metal ion using the electrochemical method was discussed. It was found that GQDs modified electrode exhibited a high sensitivity in the detection of Pb2+. In addition, the as-prepared GQDs were characterized and showed a strong and excitation-independent PL activity. In future applications, further conjugation of GQDs with antibody, sugars or peptides should be feasible, offering a versatile platform in a number of aspects such as bimodal imaging, drug delivery and targeting therapy. The GQDs will be believed to advance the development of not only graphene-based nanosensors but also biomaterial field.