Detectors are easy to be damaged by laser irradiation during optoelectronic countermeasures. Damage mechanism of semiconductor induced by high-power continuous-wave laser is investigated. The two-dimensional physical model that chemical oxygen-iodine laser (COIL) irradiates a disk target of InSb is established. The equations of heat conduction and thermoelastic dynamics are solved through integral-transform method in circular cylindrical coordinates. Transient distribution of temperature field and thermal stress field is described. The damage threshold of InSb is calculated, which is related to irradiation time and beam radius. The damage morphology of InSb is proved to be ablation, but no cleavage burst appears. It is in accordance with practice. The influence of temperature-related nonlinear parameter on damage threshold is analyzed.