Modulating the CO2 opto-galvanic voltage, signals from CO2-Na-He laser plasma have been analysed. It is shown that the amplitude of the COa opto-galvanic voltage is related to a change of the population of the CO2(0001) level and to the thermal relaxation rates of CO2 levels. Dependence of opto-galvanic voltage on the gain, intensity, dynamic resistance and temperature measured can be expressed by a solution similar to that OGE of CO molecule.