To study the thermal effect and secondary thermal radiation of infrared detection system after laser irradiation on the detector imaging, this paper uses Ansys software for thermal radiation simulation and finite element structure simulation of infrared detector. The blackbody radiation law and DO radiation calculation model are used to simulate the temperature variation with time of the optical system in the detector under different laser irradiance and the interference of the secondary thermal radiation caused by the temperature rise in the detector to the imaging of the target surface. The thermal stress and deformation in the detector are simulated by thermoelastic model. The results show that, under the condition that the detector is irradiated by 1.06 μm laser while the laser irradiance of the corrective lenses is 50 W/cm², then, the secondary thermal irradiance of the target reaches the order of 100 μW/cm² in 0.6 seconds, the infrared detector reaches saturation. After the detector is irradiated by laser, the maximum temperature of the system appears at the center of the corrective lenses, and the function relationship between the maximum temperature of the system and the exposure time is obtained by fitting, which can predict the damage of the heating structure of the detector. The maximum thermal deformation appeared at the center of the back of the mirror, which formed unequal additional optical path difference from the outside to the inside and interfered with the imaging effect of the detector. The maximum thermal stress appeared in the front center of the corrective lenses, and the linear relationship between the maximum thermal stress and the laser irradiance was obtained, which provide the prediction parameters for the thermal stress damage of the corrective lenses.