Abstract: The deep dielectric charging effect in polymeric materials is one of the most important factors threatening the satellite’s life in space environment. Deep dielectric charging process on polyimide films is studied in this paper using an electron gun with the energy ranging between 5 keV and 100 keV. Under the irradiation of electron beam with the intensity of several hundred picoamperes, the surface voltage of the polyimide film increases rapidly at the first stage and then changes slowly, reaching a final voltage of several kilo-volts, which grows with the thickness of the sample and the intensity of the electron beam under certain conditions. The charging equilibration time constant decreases with the beam intensity and the thickness of the sample. The surface voltage decays slowly when the electron beam is cut off. Resistivities obtained by charge decay method are higher than those obtained by the traditional method by one order of magnitude.