Abstract: Nickel-based superalloys exhibit excellent high-temperature strength, stable microstructure and superior corrosion resistance. They are widely applied to manufacture key high-temperature components of aero-engines, gas turbines and ultra-supercritical power units. With the continuous upgrade of industrial service conditions, the operating parameters of high-temperature equipment become increasingly harsh. The oxidation failure of nickel-based superalloys under high steam partial pressure and high stress environments has gradually become a prominent problem restricting component service life. This paper systematically reviews the research progress on oxidation behaviors and internal mechanisms of nickel-based superalloys in high-temperature steam environments. It first analyzes the influence of water vapor on the oxidation kinetics and oxide scale structure of nickel-based superalloys. The paper focuses on the evolution process of oxide scales induced by steam, in which the protective Cr2O3 and Al2O3 oxide scales transform into volatile hydroxides and non-protective spinel structures, and clarifies the essential reasons for the deterioration of scale protection performance. Then, it summarizes the regulatory mechanisms of major alloying elements including chromium, aluminum and silicon on the compactness, integrity and adhesion of steam oxidation scales. Furthermore, this study concludes the typical failure modes of nickel-based superalloys during high-temperature steam oxidation, mainly including cracking and spallation of surface oxide scales and internal oxidation of alloy matrices. Finally, it prospects several key future research directions, such as novel alloy composition optimization and design, in-situ characterization of oxide scale evolution, and simulation of multi-factor coupled service environments. This review aims to provide a solid theoretical basis for the development and performance optimization of nickel-based superalloys with excellent high-temperature steam oxidation resistance.