The paper describes a new method to determine the electrical conductivity of hot gas as well as plasma by evaluating phase shift between a high-frequency sinusoidal voltage and a correspond-ding sinusoidal current. The applicability of the new method is shown using an example of argon plasma torch. A sinusoidal high-voltage of several kV and a frequency in the kHz range range of several kHz is applied to electrodes (see figure 1). The conductive gas between the two electrodes results in a small capacitive-resistive current. Hence the electrode configuration can be regarded as a capacitor with resistor in parallel. The electrical conductivity is determined from the amplitudes and the phase shift between voltage and current using complex analysis. Measurements of gas pressure, at once allows a time dependence determination of the gas temperature.