The dissolved hydrogen (DH) in water has shown detrimental effects to the primary water stress corrosion cracking (PWSCC) performance of nickel-based alloys. In efforts to improve the understanding of the PWSCC mechanism, effects of DH on the electronic properties of the oxide film on Alloy 600 in high temperature water were studied by a combination of in-situ electrochemical techniques: dc electric resistance measurements by contact electric resistance (CER) technique and ac electrochemical impedance spectroscopy (EIS). It is revealed that the oxide film exhibited n-type semiconductivity. Dependences of the film resistance, charge transfer resistance and ionic defect transport resistance on DH obtained by the experiment suggest that increasing DH could increase the defectiveness of the film, in conjunction with an enhanced ionic defect transport in the film. The effects of DH on PWSCC are discussed in combination with the DH-dependent oxidation thermodynamics and kinetics based on the current results and the DH dependence of the oxide microstructure from literatures.