In this paper, a facile one-step approach to synthesize DNA-templated Ag/Pt bimetallic nanoclusters was developed.The obtained DNA-templated Ag/Pt bimetallic nanoclusters(DNA-Ag/Pt NCs) with diameters about 2-4 nm display a high efficient peroxidase-like catalytic activity,which can catalyze hydrogen peroxide(H2O2) mediated oxidation of the substrate,3,3′,5,5′-tetramethylbenzidine(TMB),to produce a blue color reaction.Based on this,the hairpin structure of thymine-Hg2+-thymine(T-Hg2+-T) interaction was utilized to design an unlabeled DNA electrochemical sensor for the Hg2+detection with high sensitivity and selectivity.Under the optimum conditions,the sensor showed a good linear relationship in the range of 0.65-3.5 nmol/L with a detection limit as low as 0.17 nmol/L and also exhibited an ultra high discrimination ability for Hg2+.All above properties make the sensor a promising candidate for Hg2+trace detection in real water samples.