<p>The effects of different Nb contents on the phase compositions and electrochemical properties of corrosion product films of high-strength rebars in simulated marine solution were studied by corrosion tests, surface analyses (FE-SEM, XRD, XPS), and electrochemical tests (EIS, DPP). The results showed that after different corrosion time, the corrosion product films of three rebars were mainly composed of <i>α</i>-FeOOH, <i>γ</i>-FeOOH, Fe₃O₄, and Fe₂O₃. With the increase of corrosion time and Nb content, the unstable phase <i>γ</i>-FeOOH in the corrosion product films of Nb-modified high-strength rebars was transformed into the stable phase α-FeOOH, which promoted the formation of Nb²⁺ (NbO) and Nb⁴⁺ (NbO₂) in the corrosion product films, and the Nb²⁺ (NbO) was gradually oxidized to Nb⁴⁺ (NbO₂). The existence of Nb oxides was beneficial to repair and fill the surface defects of corrosion product films and greatly promoted the formation of stable phase <i>α</i>-FeOOH, which greatly improved the corrosion potential and α/γ ratio of corrosion product films, thus improving the compactness of corrosion product films and reducing the corrosion rate of rebars.</p>