Abstract: During the environmental test of a certain type of missile seeker，its imaging primary mirror can always capture the target normally at room temperature，but it often loses the target at low temperatures. The imaging primary mirror fails because of its own surface shape with small deformation. The cause of primary mirror deformation should be determined to avoid the surface shape of primary mirror changing at low temperature in subsequent mass production. A finite element analysis software ANSYS simulation model，including screw pre-tensioning and low-temperature deformation，was established for the low-temperature failure of the imaging primary mirror，and the process of low-temperature environmental test was reproduced in the finite element software to analyze the specific failure reason of the imaging primary mirror. The simulated results show that the influence of the pre-tightening force of screws on the imaging primary mirror is much smaller than that of the uneven deformation of the primary mirror at low temperature due to the limitation of the cover screws on it. The entire process of the imaging primary mirror from assembly to low-temperature failure is recurred through simulation，which provides a sufficient theoretical basis for solving the problem about the low-temperature deformation of the imaging primary mirror，and eliminates the assembly concerns for subsequent mass production.

Key words: missileseeker, imagingprimarymirror, supportingplatform, slightdeformation, threadedconnection, modelpenetration