Ultra-high performance concrete (UHPC) was prepared via mixing water containing different chloride salts (i.e., NaCl, CaCl2 and MgCl2). The electrochemical indexes of the internal reinforcement during passivation period were measured by linear polarization, electrochemical impedance spectroscopy and cyclic polarization. The passivation behavior and evolution of steel bars in UHPC under the coupling action of different chloride salts were investigated. The results show that the reinforcement in UHPC is able to be passivated under three different chloride salt systems. The resistances of UHPC matrix, steel passivation film and steel charge transfer increase continuously with the hydration age. At the same concentration of Cl- ions, the introduction of Ca salts increases the possibility of steel corrosion to a certain extent, while the introduction of Mg salts delays the corrosion process of steel bars to some extent. The pitting corrosion sensitivity of reinforcement increases with the increment of Cl- ions concentration. At a high Cl- ions concentration, the pitting sensitivity of steel bars in Na-Ca system is greater than that in Na-Mg system.