An improved ELISA for the determination of Thyroglobulin(TG) in human serum with differential pulse voltammetry(DPV) has been developed. The enzymatic product 2,2′-diaminoazobenzene(DAA), produced from horseradish peroxidase(HRP) catalyzing the oxidation of H2O2with orthophenylene diamine(OPD), yielded a sensitive differential pulse voltammetric response at - 0.18V(Vs Ag/AgCL) in pH2.0 0.2mol/L phosphate-0.1mol/L citrate buffer at a gold electrode. The small three-electrode system was directly inserted in the well of an ELISA plate for detection. The detection limit for TG was 3.8 ng/mL, which was about four times lower than that obtained by measuring the absorbance of DAA.