Researches about thermal oxidation of IrO_x electrode for referring are not sufficient. In this study, IrO_x pH electrodes fabricated under different temperature and heating time were investigated in detail. The E-pH response, response rate, long-term stability of the IrO_x electrodes developed with temperature of 700, 750, 800, 870 ℃ and heating time of 0.5, 1, 1.5, 2 h were detected, respectively. And then, the corresponding characterizations of the fabricated electrodes were examined intensively, which including surface morphology, section morphology & energy dispersive spectrum (EDS) analysis, and electrochemical impedance spectroscopy (EIS). All the electrodes prepared by thermal oxidation had good linear near Nernst response, especially when the temperature was 750℃, 800℃ and 870℃ and the heating time was 1.0h and 1.5h. The IrO_x pH electrodes fabricated by the above heat treatment parameters had relatively fast response speed, lesser potential drift, the lower cracks on the surface oxide film, thicker film, smaller film resistance and reaction impedance. Finally, the properties of the electrodes and its relevance with preparation technical parameters and electrode’s structure and composition were discussed.