Abstract: In the design process of hypersonic vehicles, the precise prediction of transition has become a crucial challenge in aerodynamic design. However, the transition problem is quite complex and sensitive to various factors. In high-temperature hypersonic flows, transition and high-temperature gas effects are deeply coupled. The influence of thermochemical processes on flow transition cannot be ignored, especially in regions with significant velocity gradients, such as near shock waves, near-wall, and separation regions. In natural transition processes, different forms of perturbations develop differently in the flow field, subsequently affecting the transition process. Additionally, there are multiple modes in the hypersonic boundary layer, with particular attention and research warranted for the unstable supersonic modes that occur downstream in the second mode.This article investigates evolution and development of flow transition and supersonic modes under high-temperature gas effects by solving the linear PSE (Parabolized Stability Equation). Compared to the flow of calorically perfect gas, considering thermochemical processes in the flow results in a thinner temperature boundary layer, similar to a "cool wall" effect, making perturbations in supersonic modes more likely to occur. Molecular vibrational equilibrium further reduces the thickness of the temperature boundary layer in the flow, allowing the existence of perturbations in supersonic modes even under high wall temperature conditions. Additionally, under low-frequency perturbations, supersonic modes are more unstable, making the flow more prone to transition. Furthermore, in the case of flow around a sharp wedge under a Mach number of 20 and a half-angle of 6 degrees with “cold wall” and low-frequency perturbations, new variations in supersonic modes occur at specific perturbation angles.