Abstract: The corrosion resistance and semiconductor property of passive film formed on the surface of welding joint of 316LN/316L stainless steel in simulated high temperature and high pressure primary water of PWR were investigated through EIS, SEM, AES and Mott-Schottky methods. The test results show that the passive films formed on weld metal (WM) zone, heat affect zone (HAZ) and base metal (BM) zone have different corrosion resistance properties. Both the open circuit potential (OCP) and electrochemical impedance values of passive film formed on HAZ are lower than that of the other zones. This shows that HAZ passive film has the worst corrosion resistance. It’s related to film’s density, thickness and content of chromium oxide. The Mott-Schottky curve reveals that the flat band potential of BM zone passive film is -0.7 V, which is shifted negative compared with the other zones (-0.4 V). The change of E_fb was discussed as a function of anions (BO^-₃) adsorption on surface of passive film. With lower donor and acceptor density, preventing the adsorption of Cl^- in passive film, the corrosion resistance of BM zone is better than that of the other zones.