The electric conduction current characteristics of both Dupont original and corona-resistant polyimide films (100 HN and 100 CR) before and after corona-aging eight hours under electric field of lOkV/mm and 20kV/mm were measured. The results show that the conduction current of 100 CR is about one order of magnitude larger than that of lOOHN. Based on the space charge aging theory, the electric degradation threshold obtained from the space charge limit current plot is 40kV/mm for 100 CR and 35kV/mm for lOOHN, and decreases with the increasing corona-aged field. By measuring the depolarization current of the two films at 1700℃, it is observed that the decay of depolarization current of 100 CR is faster than that of 100 HN. Based on the depolarization currentcurve, the apparent carrier mobility and trap depth of l.2×10-13 m2/Vs to 3×10-14m2/Vs and l.052eV to 1.105 eV for 100CR, 1.12×10-13m2/Vs to 8×10-14 m2/Vs and l. 054 eV to 1.069 eV for 100 HN were, respectively, calculated during depolarizing.