Abstract: The energy degrader is of great significance for improving the efficiency of the proton single event effect (SEE) ground simulation tests, and the selection of the energy degrader materials is a primary problem in the energy degrader design. Four aspects that are of much concern in the proton SEE tests, i.e., the energy straggling, angle straggling, neutron background and induced radioactivity, produced by 100 MeV protons in the energy degradation process in the four common energy degrader materials （beryllium, graphite, aluminium and copper） were calculated, respectively. In terms of the calculation of the induced radioactivity, the types, activities and residual dose rates of the radionuclides generated in the materials were included. According to the above calculation results, combined with the requirements of the proton SEE tests, the applicability of the four materials as the energy degrader material for 100 MeV protons was analyzed and compared in the case of the same energy degradation. Finally, aluminium was selected as the energy degrader material for 100 MeV protons employed by the proton SEE ground simulation test facility on the 100 MeV proton cyclotron of China Institute of Atomic Energy.