Abstract: The low-energy proton irradiation test on the F46/Ag second surface mirrors was performed in a ground-based space irradiation environment simulator. The results demonstrate that the 30 keV proton irradiation can lead to a significant degradation of the optical properties. The changes of the solar absorptance increase linearly with the fluence and the changes of the reflectance at the 350 nm wavelength increase exponentially with the fluence. The distributions of the ionization and the non-ionizing energy loss in different depths are acquired by the Monte Carlo method. It is found that the energy is transferred from protons to atoms of the F46 mainly through ionization during the irradiation and the surface layer absorbs the most energy under 30 keV proton irradiation. The quantum chemistry calculation indicates that the 30 keV proton irradiation can induce the debonding of C-F and C-C in the surface layer and the energy required in the bond breaking reactions is much less than that of the protons transferred to the F46 molecules. The XPS results show that the proton irradiation induces several debonding and recombination reactions in the surface layer, leading to the formation of free radicals and molecule fragments as well as the decrease of F and surpluses of C, as in agreement with the quantum chemistry calculation.