At hypersonic speeds exceeding Mach 10, the intense compression of air by shock waves generates a high-temperature plasma sheath. In such plasma environments , the Coulomb screening effect among charged particles induces ionization potential depression (IPD). However, how this microscopic mechanism modulates macroscopic flow parameters—such as temperature, density, and pressure—as well as electromagnetic properties including electron density and plasma oscillation frequency, remains insuffciently explored. To address this, the present manucript investigates the IPD effect through theoretical modeling and numerical simulation. First, based on atomic energy level calculations and the local thermodynamic equilibrium (LTE) assumption, we calculate the plasma coupling parameter across a temperature range of 0.8–5 eV and a density range of 0.1–20 times the sea-level atmospheric density. On basis of the coupling parameter, we determine the applicable regimes of the Debye-Hückel (DH) and Stewart-Pyatt (SP) models for the hypersonic environment. Second, integrating these IPD models with the Rankine-Hugoniot relations, we analyze the effect of IPD on the flow characteristics in the stagnation region. The results reveal that IPD significantly alters the ion fraction, thereby modifying the thermodynamic state of the post-shock air. Third, to extend the analysis from equilibrium to non-equilibrium conditions applicable to real flight, we incorporate the IPD effect into Computational Fluid Dynamics (CFD) simulations. Specifically, the activation energy in the forward reaction rate is modified by IPD, while the reverse reaction rate is coupled via the Saha equation for consistency with chemical equilibrium. Using the RAM C-II vehicle configuration as a benchmark case, we conduct numerical simulations at an altitude of 50 km and a velocity of Mach 32. Results show that IPD shifts the shock wave closer to the vehicle surface and increases the electron number density in the wake region. In contrast, the effects on wall pressure and aerodynamic drag are relatively minor. Importantly, the elevated electron density leads to an increase in the plasma oscillation frequency, which directly alters the critical threshold for communication “blackout”. Consequently, neglecting the IPD effect results in an overly conservative prediction of the blackout envelope. This work elucidates the microscopic-to-macroscopic pathway by which Coulomb screening influences flow field thermodynamics and electromagnetic properties, specifically through the modulation of ion abundance and energy deposition patterns. These results provide a theoretical basis and a technical reference for assessing the thermal environments of hypersonic vehicles and modeling plasma sheaths under extreme conditions.