The method of electrochemical determination of oxygen partial pressure in ionic melts includes providing a metal/metal oxide reference electrode consisting of an electrode body made of a metal selected from the group consisting of Mo, W, Hf, Nb and Ta and alloys thereof and a layer of an oxide of that metal on the electrode body; immersing a pure platinum electrode and the metal/metal oxide reference electrode in a glass melt; measuring a potential across the metal/metal oxide reference electrode and the pure platinum electrode immersed in the glass melt to obtain a measured potential characteristic of the oxygen partial pressure in the glass melt; obtaining a calibration curve relating the potential across said reference electrode and the pure platinum electrode to the oxygen partial pressure in the glass melt as a function of temperature; and obtaining the oxygen partial pressure in the glass melt from the measured potential and the calibration curve. Either the calibration curve is obtained experimentally by immersing a Zirconium dioxide electrode in the glass melt and measuring a potential difference between the metal/metal oxide reference electrode and the Zirconium dioxide electrode at a plurality of temperatures or theoretically from thermodynamic data for the metal/metal oxide reference electrode.