Abstract: Arcjet attracts more and more researchers today, because its specific impulse is higher than the thrusters with chemical propellants. A electrostatic probe diagnostics system used in vacuum environment, for the measurement of the electronic temperature of the Arcjet plume plasma is established. The electronic temperature of the Arcjet plume, with argon as the propellant , is measured by this system, and the axial and radial distribution electronic temperature of plume is obtained. The result shows that the electronic temperature is much higher than the heavy particle temperature in the axis of the Arcjet plume.