Graphene quantum dots (GQDs) with a size of < 10 nm were generated from graphene oxide sheets by exploiting the scissor cut effect after sono-and photo-chemical treatment. During this process, hydrogen peroxide was added as the only chemical reagent. A strong cathodic electrochemiluminescence (ECL) signal was generated by applying a cyclic voltammetry scanning on glassy carbon electrode in a mixture of GQD and potassium persulfate. The ECL properties of GQD/K(2)S(2)0(8) coreactant system were studied in detail and a possible mechanism was prnrosed which re.realed that the signal was mainly dependent on the presence of the reduction of GQD and dissolved oxygen. Furthermore, the ECL signal was found to be quenched by H2O2, a product of enzymatic oxidation of glucose. Therefore, an ECL glucose biosensor was prepared by decorating a film consisting of glucose oxidase, chitosan and GQD on a glassy carbon electrode. Under the optimized conditions, the ECL decreased linearly in the 1.2 to 120 pmol.L-1 glucose concentration range, and the detection limit was as low as 0.3 pmol.L- 1.