To generate the hypervelocity (above 5 km/s) test flow for the experimental study of reentry physics, a shock-expansion tube or tunnel is the only qualified test facility by far. In such a facility, the working gas shall be compressed by an extremely strong shock wave, e.g., Ms=27.7 for the 8 km/s test condition. Therefore, thermo-chemical nonequilibrium phenomena may occur in the gas post the shock wave. Such phenomena, consequently, can incur difficulties in diagnostic and measurement to experimental study, and instability problems to numerical analysis on the other hand. The present paper will focus on the numeric-aid diagnostics of the flow conditions.