Abstract: The principle and the theory of charge characteristics of xenon working gases for the satellite electric propulsion system are discussed. A technique to study the charge characteristics of xenon working gases is put forward. Physical experiments including the saturated vapor pressure and the xenon in the phase of gas and in super-critical state are carried out. A new saturated vapor pressure formula is obtained. The critical pressure of the xenon is obtained by a linear fitting method, and experimental data are compared with testing data obtained by other research institutes. The relative deviations between the xenon saturated vapor pressure testing value and the NIST equation are less than 0.2%. The maximal deviation of the NIST formula takes place near the critical region, with a value of 6 kPa. The experiment helps to establish a mathematical model of the xenon working gas charge characteristics.