Abstract: Firstly, a method based on the Geant 4 software is introduced. It can calculate the electric field arisen from internal charging effects under the special space environment. Secondly, the space electron environment CRRES satellite was located on was analyzed and used to simulate the internal charging effects. Lastly, the attempt has been made to compare the data from the CRRES IDM space experiment and the data from simulation results. This comparation showed that the calculation method is validated and some basic conclusions about the space environment which causes the internal charging effects are drawn. The calculations show that the high-energy electron flux/energy spectra is the primary cause of discharges. The material characteristics, especially the RIC （Radiation Induced Conductivity） and dose rate factor kp are very important to the steady state electric field. For studying the internal charging effects, need to mensurate these material characteristics accurately in laboratory.