Many H+ response characteristics of Iridium oxide electrode were described in this paper. The linear relationship between open-circuit potential and pH value, decisive factors to response rate were studied in detail. The hysteresis effect were also investigated, furthermore, many determination technologies, such as cyclic voltammetry, SEM, XPS were used to analyze the element valence and composition or to decide the rate of inner and outer surface, as well as to observe the morphology of the oxide film, from which the relationship between hysteresis effect and film thickness as well as morphology was discussed, finally, the response mechanism of the hydrous iridium oxide electrode were suggested.