The cathodic electrochemiluminescence (ECL) behavior of Eosin Y (EY)-peroxydisulfate (S2O82-) system at a glassy carbon electrode (GCE) was studied under cyclic voltammetric conditions. Two strong ECL peaks, ECL-1 and ECL-2 were observed in cathodic and anodic scan process respectively under the potential scan range 0 to -2.0 V. The effects of pH value, S2O82- concentration on the ECL intensity were investigated and the possible mechanism for the ECL behavior of EY-S2O82- system was proposed. Based on the stable cathodic ECL of EY-S2O82- system and quenching effect of guanine on the ECL-1 and ECL-2 intensity simultaneously, the logarithmic plot of the inhibited ECL-1 and ECL-2 versus logarithmic plot of the concentration of guanine was linear over the range of 5.0 x 10(-6)-1.0 x 10(-4) mol/L with a correlation coefficient of 0.998 and 0.996, respectively. (c) 2012 Elsevier B.V. All rights reserved.