Abstract: TiAlON-based materials applied in solar energy were studied by spectroscopic ellipsometry. Different dispersion formulae such as Cauchy, Lorentz and Tauc-Lorentz models were applied to fit the experimental data of insulation TiAlON film and its optical constants were obtained. The application of the different dispersion models and film structures were compared in various spectral ranges. It is demonstrated that the Tauc-Lorentz model is more suitable for fitting ultraviolet to near-infrared spectroscopy. The results suggest that spectroscopic ellipsometry is a reliable method for characterizing the TiAlONbased material system, and can be used for further study on the optical properties of multi-layer film stacks.