Abstract: In this paper,two calibration methods are introduced for working gas micro-flow calibration for space electric propulsion system.One is absolute pressure constant volume rise pressure method and the other is differential pressure constant volume rise pressure method.Based on two calibration methods,a new calibration apparatus for working gas microflow to space electric propulsion system is designed,and the apparatus can be roughly divided into seven parts,pumping system,calibration system,volume measuring system,stabilizing pressure system,multiple working gas path switching system,constant temperature and baking system,data acquisition system.Its calibration range is from 5×10^-5to 5×10^-1Pa·m³/s,inlet pressure is from 0.2 to 0.5 MPa,expansion uncertainly is less than 2.0%(k=2),calibration gases are Xe,Kr,Ar,He and N₂.The performances of present calibration apparatus meet the demand for practical requirement for space electric propulsion system.