We demonstrate that the GaAs/A1GaAs nanowires (NWs) ensemble is fabricated into photo-detectors.Currentvoltage (Ⅰ-Ⅴ) characteristics are measured on GaAs/A1GaAs core-shell ensemble NW photo-detectors at room-temperature before and after 1-MeV proton irradiation with fluences from 1.0 × 1013 cm-2 to 5.0 × 1014 cm-2.The degradation of photocurrent suggests that the point defects induced by proton radiation could cause both carrier lifetime and carrier mobility to decrease synchronously.Comparing with a GaAs quantum well,the degradations of light and dark current for the irradiated NWs photo-detector indicate that NWs material is a preferable potential candidate for space applications.