Abstract: To determine the charging characteristics of the HEO satellite, a model is constructed based on the FLUMIC model of the ESA in the manner of electrons in the radiation belt, as in the HEO electron environment evaluation. The main characteristics of the deep dielectric charging on the HEO satellites are studied. The results are compared with those in the GEO. It can be concluded that the daily-averaged electron flux of the HEO and the GEO are in the same level, while the instantaneous flux sees significant fluctuations, which might increase the charged potential and the risk of the internal charging. It is shown that the average charged potential in the HEO is about 1.3 times higher than that in the GEO, while the instantaneous potential has a 12-hour period. The results demonstrate that the peaks of the charged potential have tens of minutes delay in contrast to the peaks of the electron flux. It is recommended that a thicker shield layer and a thinner dielectric layer can mitigate the fluctuations of the charged potential and reduce the risk of the internal charging during HEO missions.