Abstract: The effects of chloride concentration and dissolved oxygen on the high-temperature electrochemical corrosion behaviors of 304 stainless steel sheets were investigated in simulated pressurized water reactor (PWR) primary water. The results of potentiodynamic polarization measurements reveal that the chloride ion mainly affects the second passivation region under high potential, but little effect under low potential. Oxide film chemical content analysis by X-ray photoelectron spectroscopy (XPS) shows that the second passivation properties are closely related to the Fe/Cr ratio of the oxide film. Electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) results show that, when the chloride ion concentration increases, the oxide film resistance decreases, the size of oxide particles and the gap between oxide particles on the outer layer increases and the corrosion resistance decreases. Besides, with the increase of dissolved oxygen, the corrosion potential increases, the passive current density decreases, the passive potential region shrinks, and the oxide film resistance gradually increases.