This paper reports a two-step seed-mediated synthesis of gold core@silver shell nanoparticles (Au@Ag NPs). The plasmonic properties of Au@Ag NPs were controlled through the etching effect of H₂O₂ generated from the oxidation of glucose. Therefore, we used Au@Ag NPs as surface-enhanced Raman scattering (SERS) substrates and 4-mercaptobenzoic acid (4-MBA) as the Raman tag to detect glucose concentration. This method exhibits a rapid detection process (5 min), a determination range from 10⁻¹ M to 10⁻⁶ M and a detection limit of 10⁻⁶ M, which indicate that Au@Ag NPs can serve as sensitive SERS sensors for clinical detection of blood sugar.