Radiation effects of 1 MeV electron on a home-made type of triple-junction GaInP/GaAs/Ge solar cell have been investigated. The results indicate that the GaInP/GaAs/Ge solar cell has high efficiency and high radiation hardness. The final-to-initial maximum power ratio (P/P0) of the GaInP/GaAs/Ge cell was 80.4% at a fluence of l × l015 cm-2. The spectral response of the GaInP top subcell showed little degradation, and this was not a limitation for GaInP/GaAs/Ge cell performance. The GaAs middle subcell Isc, however, presented serious degradation. The degradation of GaInP/GaAs/Ge solar cell is due primarily to the GaAs middle subcell.