Abstract: According to the structure of IR detector and the theory of thermal conduction, thermal damage of IR detector irradiated by optical maser of laser jammer was investigated. InSb photovoltaic detector was selected as a research detector. The Thermal Model was developed based on the structure of InSb detector. In this model, the detector was divided into three layers which included InSb chip, glue and copper substrate. The thermal conductivity functions of each layer were different due to various material's conduction coefficient values. The distribution in space of incident laser beam was Gaussian profile, supposing the incident laser irradiated on the top layer, and set the initial value parameters and boundary conditions. The initial temperature of the detector was 77 K and the boundary conditions were Neumann type. The multi-layer thermal models for laser damage were solved by PDE-tool. The plot of temperature rise was acquired by specifying a group of typical laser parameters through simulation. Key factors consisting of the power of optical maser, the irradiated time and the distance between the infrared detectors and optical maser were deeply researched. Through Orthogonal experimental design, a series of contrastive figures were obtained. The thermal damage effects were analyzed on basis of these data. The simulation results confirm that the detector absorbs the energy of the laser and the temperature rise centralized on InSb materials and the glue. Since the glue's conduction coefficient value is low, the glue is poor at thermal transfer, so the temperature drops dramatically in the glue layer. When the power of continuous laser is 50 W, the irradiated distance is 200 m, and the irradiated time is 3 s, the infrared detector suffers soft damage. The power of density continuous laser is lower than the pulsed laser, as a result, the optical maser doesn't bring about long-lasting destructive effects.