Anintense cathodicelectrochemiluminescence(ECL) is reportedfrom a polarized glassy carbon electrode (GCE) in peroxydisulfate solution. After the polarization in 1M Na2SO4 at the potential of - 3.7V for 3s, carbon nanosheets (C-NSs) were in situ grown on the surface of theGCE. Measured in 100mM K2S2O8 solution, the ECL intensity of the GCE/C-NSs is 112-fold that of a bare GCE. The ECL spectrum revealed that the true ECL luminophore in the GCE/C-NSs-peroxydisulfate system is O2/S2O82- which is promoted by C-NSs. When Cu2+ was electrochemically enriched and reduced to Cu(0) on the catalytic sites of C-NSs, the ECL from GCE/C-NSs/Cu in K2S2O8 solution was decreased with increasing logarithmic concentration of Cu2+ in the range from 10pM to 1μM, with a limit of detection (LOD) of 3pM. An immunoanalysis method isproposed via a biometallization strategy using CuS nanoparticles as the tags and carcinoembryonic antigen (CEA) as the model analyte. After the immune recognition in the microplate, the CuS tags in the immunocomplex were dissolved and the resultant Cu2+ was electrochemically enriched and reduced on the catalytic sites of C-NSs, quenching the ECL intensity of GCE/C-NSs-O2/S2O82- system. The proposed ECL immunoanalysis methodwas used to quantify CEA in actual serum samples with anLOD of 1.0fgmL-1, possessing the advantages of simple electrode modification, high sensitivity and good reproducibility.