Abstract: The energetic charged particles in space can lead to deep dielectric charging on exposed electric cable bundles outside the satellite skin. Based on the principle of the current conservation, the process of deep dielectric charging is analyzed using the particle transport simulation software Geant4 and the radiation induced conductivity formula. In the GEO severe electron flux environment, the three-dimensional simulation is carried out for the deep dielectric charging of exposed electric cable bundles. It is shown that the balanced potential is negative, the peaks of the potential and the electric strength appear on the external and internal surfaces of the outermost cables in a bundle, respectively. Little effect on the internal charging results is shown whether the dielectric layers of cables in a bundle are connected to each other or not and how many cables are in the bundle. It is the dielectric bar binding the cables that involves high discharging risks. When this dielectric bar's thickness is 0.8 mm, the charging potential and the electric strength are about -10³ V and 4×10⁶ V·m^-1, respectively. What's more, the potential and the electric strength will increase considerably as this thickness is enlarged.