Abstract: The method of determining temperature of gas and particles in a conductive working medium of a magneto hydrodynamic generator comprises the steps of measuring values .phi.1, .phi.2 and .phi.3 of radiation fluxes from a primary radiation source, the working medium of the MHD generator and a working medium subject to radiation from the primary source at least on two wavelengths .lambda..sub.1 and .lambda..sub.2 ; and computing the temperature of gas and particles from relationships obtained by a generalized method of reversing spectral lines. The wavelength .lambda..sub.1 is found at the center of a resonant line of an alkaline metal spectrum. Selection is made during measurements of those groups from a sequence of the obtained groups of values .phi.1, .phi.2 and .phi.3 at a permissible error k.