Abstract: In order to improve the optical performance of optical window in aerial remote sensor, thermal-optical evaluation to fused silica optical window surrounding hypersonic was analyzed. The flight environment of optical window was analyzed. Based on the theory of aerodynamics, the relation between convection heat transfer coefficient and mach number was calculated. The temperature distributing of optical window was simulated by heat flux density, the optical path difference caused by the temperature difference between the inner and outer surfaces was calculated, and the influence of thermal deformation of the optical window on optical transfer function was analyzed. The study result shows that the optical path difference caused by thermal deformation of the optical window is 130.5 nm, which is under 1/4. The simulation result meets the requirements of the optical design. The above result discussed in this paper can be used as a reference for other optical window designs.