Abstract: The optical properties of TiO2 thin film prepared by electron beam evaporation with different craft parameters are studies.On the base of experiments,the main factors of affecting the refractive index of the TiO2 thin film deposition assisted by ion beam have been found out.Function relation of TiO2 refrative index,oxygen pressure and deposition speed have been gained,besides infrared spectrum.Refractive indices of TiO2 thin film deposited in ioned and molecular oxygen are compared.