Abstract: During the high speed flight of a missile, its dome was subject not only to high temperature, but also to load caused by pneumatic calefaction. In this work, the deform of both the planar window and the spherical dome made of ZnS material were ANSYS-based calculated at a temperature of 500℃ and at the pneumatic pressure of 4 atm. Furthermore, the effect of deform on IR imaging system quality were analyzed by ZEMAX optical design software. As to the IR long wavelength imaging system with optical parameters, field of view of 13, focal length of 70 mm, and F number of 1, effect of pneumatic calefaction on imaging system quality was discussed. It has been demonstrated that the modulation transfer function (MTF) (16 lp/mm) in all field of view is insensitive to deform of IR planar window. However, deform of spherical dome could cause MTF declined by maximum 2.56%.