Abstract: space plasma characteristics are low temperature, low density, and uniform in Low Earth Orbit (LEO). The plasma influence on the spacecraft, and the configuration and facility of the double ECR plasma were described in detailed. The standard Langmuir probe about plasma characteristics was used in experiments. Some plasma parameters were got including plasma space potential, and floating potential. Electron temperature electron density and so on. The electron density is between 10⁶ cm^-3 and 10⁸ cm^-3. Electron temperature is between 1 eV and 10 eV. So it meets the mission of LEO space plasma.