A simple and rapid mercury ion selective electrode has been well constructed. The Au/1-UDT electrode for sensing Hg2 + has a sensitivity of 28.83 ± 0.4 mV/− pC. The ISE method has a detection limit of Hg2 + down to 4.5 × 10− 9 mol L− 1. A mechanism with density functional theory for recognition of Hg2 + is developed. The quantum chemical computation demonstrates Au-Hg metallophilic interaction.