The optogalvanio signal (OGS) in CO2-N2 discharge tube irradiated by CO2 laser has been measured by a narrow band-pass filter, and the electron energy distribution (EED) has been measured by a second-order differential circuit. It is considered that OGS in CO2-N2 discharge tube is generated through step ionization when CO2 and N2 molecules in electric excited states are disturbed, and the rate of step ionization is changed by 10.6μm laser irradiation.