Abstract: Compared with the result of Monte Carlo method, there are some problems when the existing internal charging threat assessment model (DICTAT) calculates the dose rate of electrons. In order to correct the problems, the Tabata’s depth-dose formula of electron was introduced and DICTAT was reconstructed, and a new DICTAT was developed. Afterward, the charging electric field and potential of a series of polyimide slabs with different thicknesses were calculated by new model, DICTAT and 3D simulation tool, and then comparison analysis and interpretation of calculation results were made. The results show that the calculation result of new model is consistent with that of the 3D simulation tool, which can assess internal charging threat more accurately.