Abstract: A tin doped indium trioxide conducting electrode coated with mercury film (Hg ITO) was obtained and an optically transparent thin layer electrochemical cell with Hg-ITO as electrodes was designed. The optical and electrochemical properties of Hg-ITO electrode and the cell were tested. In aqueous solutions, the negative potential range of this Hg-ITO electrode was 700mV larger than that of ITO electrode. The Hg ITO electrode showed the electrochemical properties of Hg electrode. This cell can be used for the spectroelectrochemical studies of electrochemical processes with larger negative reduction potentials and the electrochemical analysis of metallic ions.