When governing equations of a one-dimensional mixing theory are solved in the two limited cases, vibrational-frozen and vibrational-equilibrium flows, actual flow parameters such as static temperature and velocity at a optical cavity region in mixing gasdynamic lasers can be determined from measured static pressure at the cavity point. A measured static temperature at the laser excitation region determined by the present method is 268'K with the theoretical uncertainty of d:1.9%. This value of the temperature is well agreed with a temperature estimated by a rotational population distribution of carbdn dioxide molecules. It is revealed from a theoretical consideration that the uncertainty of the flow parameters determined this method is less thdn ilO% even at a high stagnation temperature (-3000'K) and any higher Mach number at the cavity section.