Abstract: According to characteristics of IR systems, the intensity distribution of an optical element in IR system is analyzed by optical gain. The optical element at focus plane is damageable element by laser. The damage mechanism of the detection and guidance functions of the IR system from the damage of optical element radiated by high power laser is presented. Based on the analysis on the spectrum responding characteristics analyzed by IR filter, detector and signal processing electrocircuit, the soft damage mechanism of resulted output signal disturbance in IR system radiated by low power laser, and the detection function disability in laser radiation time caused by laser are presented. The validate experiment of disability in IR system radiated by laser has been developed, the invalidation me