For the test of space radiation hardened parts, quantitative analysis of space environment in which satellites are operating is performed. From these data, it can be suggested that how to control the 20MeV proton beam to simulate the space environments. To this end, energy degrader method is suggested and then, 8 candidates material for energy degrader are simulated by SRIM code. Finally, $SiO_2$ which is basic material for semiconductor is simulated under 20MeV proton beam by MCNPX code to see in which parts how much energy is deposited.
