Abstract: With the increasing of flight Mach number, the high-temperature gas effect of air has becoming remarkable, which has significant impacts on the aerodynamics and aerothermodynamic characteristics of hypersonic vehicles. Because of the complex mechanism and numerous key parameters of high-temperature gas effect, it has not been fully studied at home and abroad. When the high-temperature gas effect occurs, multiple nonlinear physical processes are coupled together. However, ground tests and numerical simulations can not decouple these processes and can not explain the key physical mechanisms. To solve this problem, a new two-step asymptotic approximation method combining theoretic analysis and numerical simulation is proposed. In this method, the oblique shock relation with vibration excitation effect is obtained by Newton iterative method, then the results are used as the boundary conditions of the boundary layer and it is solved numerically. By using this method, the effect of vibration excitation on the aerodynamics and aerothermodynamic characteristics of a two dimensional wedge is studied. The results show that, the vibration excitation process has great effect on the shock angle, the temperature, density, Mach number, and Reynolds number behind the oblique shock, but little influence on the pressure and velocity. The inviscid flow behind the oblique shock is coupled together with the boundary layer flow. The changes of multiple physical quantities, including the increase of velocity and the decrease of the temperature behind the oblique shock, and the decrease of the boundary layer thickness due to the increase of the Reynolds number, have an effect on the friction and aerodynamic heating in the boundary layer. Comparing with perfect gas model, vibration excitation increases the wall friction and decreases the wall heat flux of the wedge. By influencing the shock layer and the boundary layer respectively, the effects of vibration excitation on heat flux are strong coupled, while they are weak coupled on friction.