A surfaceenhanced Raman spectroscopy (SERS) technique based on functionalized Au@Ag nanorods (Au@Ag NRs) was established to quantitatively detect Hg2+ in aqueous solutions.In the presence of Hg2+,its coordination with 2,5 dimercapto 1,3,4-thiadiazole (DMCT) on the surface of Au@AgNRs caused the aggregation of SERS detection probes,resulting in a “hot spot” effect,leading to the SERS signal of DMCT increased at 1 360 cm-1.The increased SERS signal showed a good linear relationship with Hg2+ in the concentration range from 0.1 to 10 μg/L :Y=195.49384X+1676.23663(R2=0.991).The detection limit was as low as 17 ng/L,much lower than that of the Hg2+ content(1 μg/L) in drinking water specified by World Health Organization(WHO).The results of spiked recovery test carried out in the actual water sample showed that the spiked recoveries of Hg2+ were from 100.1% to 106.5%,and the relative standard deviations were from 1.23% to 7.99%.The Hg2+ sensing detection technique with accuracy,rapidity and high sensitivity based on SERS has an effective application for quantitatively detecting Hg2+ in real water.