In this paper, the basic laws of spectral response, open-circuit voltage and short circuit current of GaAs/Ge solar cells are obtained by ground simulation irradiation test under the different-energy electrons’ irradiations, such as 1, 1.8 and 10 MeV. The carriers’ transport mechanism in cells is analyzed using the PC1 D simulation program. The variations of the majority carriers’ concentration and the minority carriers’ diffusion length with the irradiation particle fluence are obtained in GaAs/Ge solar cells under different-energy electrons’ irradiation. Majority carriers’ removal rate and minority carriers’ diffusion length damage coefficient are calculated under different-energy electron irradiations. The results show that majority carriers’ concentration and minority carriers’ diffusion length decrease with increasing the incident electron fluence. The majority carriers’ removal rate and the damage coefficient of minority carriers’ diffusion length increase with increasing the electrons energy. The majority carriers’ removal effect and the minority carriers’ diffusion length shortened are the main reasons of open-circuit voltage and short circuit current degradation of the solar cells, respectively.