Abstract: Cr-Cr2O3 cermet films were deposited by DC reactive magnetron sputtering under different target currents. The optical constants of the films were measured by a spectroscopic ellipsometer in VISNIR. The optical constants of Cr-Cr2O3 cermet films were theoretically calculated with the modified M-G (Maxwell-Gannett) theory, and the calculated results were compared with the experimental data. The results indicate that with the increase of target current, the metal volume fraction and the radius of the metal particles of Cr-Cr2O3 cermet films increases, and the metal particles become oblate spheroids. The results obtained by the modified M-G theory agree with the experimental results.