Studying more precise and efficient measuring-method for determining optical parameters of thin films plays a guiding role in improving design and optimizing preparation process of optical thin films. Several traditional measuring-methods were introduced briefly in this paper, and a new measuring-method was deduced combined envelope with the full spectrum inversion method fitting. In this method, optical parameters of a single layer were calculated approximately with envelope method, and according to the results, the upper and lower limits of the optical parameters were estimated for the full spectrum inversion method fitting firstly. Then, the physical model of the new method was established. After that, the optical parameters of thin films were solved by choosing a comprehensive optimization algorithm. Finally, the validity of the new method was validated through measuring of TiO2、SiO2 single-layer and G|0.5HLHL0.5H|A(H-TiO2，L-SiO2) multilayer. Besides, the measurement accuracy, efficiency and stability of the new method were also analyzed.