Abstract: In order to satisfy the requirements of the reliability evaluation during the electric propulsion being developed and the interaction analysis between electric propulsion and spacecraft,an electric propulsion plume diagnostic system integrated Faraday probe and Langmuir probe and Retarding potential analyzer with power processing unit and measurement and control software was developed.The performance verification test demonstrated with LIPS200 ion thruster show that the typical characteristic curve and diagnostic results can be obtained with all probe.The ion current density measured with FP at 150 mm from exit plane of the thruster ranges from 0.02 mA/cm²to 0.80 mA/cm²,and the main ion beam diameter with the density between 0.66 mA/cm²and 0.80 mA/cm²is 90 mm.The plasma parameters measured with the cylindrical LP and the planer LP at 500 mm from exit plane of the thruster show that the electron temperatures are respectively 1.3 eV and 1.2 eV,and the electron densities are respectively 2.1×10¹⁵m^-3and 2.0×10¹⁵m^-3,and the plasma potentials are same value of 4.6 V.Ion energy-per-charge measured with RPAat 500mm from exit plane of the thruster is 1001 eV±44 eV,which is correct by comparing with 1 185 V of total accelerating voltage of LIPS200.