The present work studies the variation of refractive index of titanium dioxide thin films due to changes in the evaporation rate during the deposition process under high vacuum. The experiments were done by depositing thin films on a glass disk of 45 cm in diameter for different deposition rates. To characterize thin films the spectral transmittance in the visible range was measured at different points along of two perpendicular radii. The refractive index profile was then determined from these data by using an inverse synthesis method. The results permitted us to obtain the refractive index variation as a function of evaporation geometry for different deposition rates.