Abstract: After configuration size and combing type of aerial electro-optical equipment have been confirmed, thickness dimension is critical to its imaging performance. In this paper, window designing subject has been described and analyzed from three aspects - design variable, combing type and applied loads, plane window's thickness is specified as design object based on structural stiffness and RMS wave-front errors. based on the first order structural resonance frequency and the RMS wave-front errors of temperature and pressure effects, window thickness's dimension range has been quantitative solved and is <11.9 mm, 18.4 mm>. Integrated analyzing process has been proposed aiming at window assembly's performance in synthetic conditions, the first order structural resonance frequency of optical window assembly is 151 Hz, RMS wave-front error is less than 1/10 reference wavelength with effects on composite load-flow field and gravity and vibration in operation. Window's RMS wave-front error obtained by laboratory test is less than 0.07 reference wavelength, Images of vibration and flying test are stable and clear. Tests results indicate that designing and analyzing method of window thickness dimension is right and effective.