The characteristics of Al nano film were studied by using AFM and spectroscopic ellipsometer methods.It was indicated that the surface roughness of sputtered Al nano film,from 1.216 nm(rms) at 0.4 Pa to 3.521 nm at 1.6 Pa,is proportional to the sputtering Ar pressure.The refractive index,extinction coefficient and reflectivity of Al nano film all decrease as the sputtering Ar pressure increases.The above phenomenon is related to the change of Al nano film structure.In most cases,the reflectivity of Al nano film is more than 85 %.It was also indicated that the surface roughness of sputtered Al nano film increases when the sputtering power increases,from 0.486 nm at 1 000 W changing to 2.014 nm at 2 500 W.However the optical constants of Al nano film are not sensitive to the sputtering power.