Zinc addition technique is widely used in the first circuit of boiling water reactor (BWR) and pressurized water reactor (PWR) to lower the stress corrosion cracking and radioactive pollution of nickel-base alloys. An oxide film of Inconel600 with semiconductor properties was formed in high temperature water. And the semiconductor properties were changed by very little amount of zinc addition. Photoelectrochemical response and capacitance measurement were employed to investigate the oxide films formed on Inconel600 with/without zinc addition. The photocurrent of the oxide film was plotted as a function of photon energy, for separating into several parts, which can be derived from Fe₂O₃ with a band gap energy 2.2 eV, Cr₂O₃ 3.5 eV, Fe_xNi_{1－xCr2O4 4.1 eV besides ZnO 3.2 eV. For steady photoelectrochemical responses, the oxide film formed with zinc addition exhibited anodic photocurrent at open circle potential while the film without zinc exhibited cathodic photocurrent. Mott-Schottky plots indicates a negative movement of the flat band potential of the oxide film on Inconel600 with zinc addition to the film without zinc. At the same potential, the higher (space charge capacitance, CSC) indicated a more compact oxide film of Inconel600 with zinc addition in the high temperature water. It comes to a conclusion that the photoelectrochemical responses is a sensitive and effective method to investigate the oxide phase in the oxide film on alloy.}