Abstract: Under the environment of vacuum and heat sink, the effects of the irradiation of protons with an energy of 60 keV on the optical specular reflectance of Al reflector are studied. The experimental results show that the specular reflectance of the Al film reflector is significantly affected by the irradiation. With increasing fluence, the specular reflectance decreases monotonously. At a low radiation fluence of 1×10¹⁶ cm^-2, the specular reflectance is decreased but slightly, and the change firstly occurs in the ultraviolet region. With a further increase of fluence, a significant decrease of the specular reflectance occurs particularly in the wavelength range of 250~800 nm. The reason for the decrease could be attributed to the appearance of ripples and hillocks on the surface of the Al mirror after the proton irradiation.