In view of the crack problem of 800mm optical glass in a supersonic wind tunnel during the test, the causes of cracks are analyzed in detail, and the structural form and assembly method of optical glass are optimized. Firstly, the thickness of glass is reduced to meet the strength requirements, so as to avoid the stress concentration caused by the large difference of the axial temperature gradient. Then, a low-stress stepped optical glass that is easy to install and adjust is designed to reduce the damage to the optical glass due to installation and operation errors, and Solidworks software is used to calculate the stress difference between the two structural forms under appropriate preload and internal and external pressure difference. Finally, Abaqus software is used to analyze the influence of temperature on optical glass during the wind tunnel test. The results show that the pressure difference has little effect on the strength of the observation window, and the stress of the stepped optical glass is less than that of the original structure. The temperature drop in the case of high Mach number and pressurization will cause stress concentration in the middle of the observation window.