Super-resolution nea-field structure (super-RENS) is one new optical storage technique which can overcome the optical diffraction limit to write and read the recording pits by a functional thin film structure. In general, the performance of super-RENS is mainly determined by the mask material. The microstructure and morphology of the as-deposited Sb2Te3 film are observed by transmission electron microscope (TEM). The dependences of optical properties on thickness of the Sb2Te3 films are carried out by ellipsometer and optical spectrometer, respectively. The results indicate that the as-deposited Sb2Te3 film is partly crystallized. Moreover, the optical properties change a lot within a certain thickness range. The extinction coefficient and refractivity of Sb2Te3 film decrease with the increase of thickness when the thickness is very small. Moreover, the optical constants tend to be stable when the thickness reaches a critical value. This critical value is 80 nm for the extinction coefficient, and 50 nm for refractivity of the film. The relationship betwean the optical property and thickness of Sb2Te3 film can be explained by the continuity of film structure.