This paper reports the high-energy proton irradiation effects on GaAs/Ge space solar cells. The solar cells were irradiated by protons with energy of 5-20 MeV at a fluence ranging from 1 x 10(9) to 7 x 10(13) cm(-2), and then their electric parameters were measured at AM0. It was shown that the I-sc, V-oc and P-max degrade as the fluence increases, respectively, but the degradation rates of I-sc, V-oc and P-max decrease as the proton energy increases, and the degradation is relative to proton irradiation-induced defect Ec-0.41 eV in irradiated GaAs/Ge cells. (C) 2002 Elsevier Science B.V. All rights reserved.