Based on the open-circuit output function of a photovoltaic (PV) detector, the response model of a HgCdTe detector that is operable in the long-wave, medium-wave, and short-wave bands is established. Simulation results show that the temperature rise generated by laser irradiation reduces the output of the detector, and the detector produces a saturated output immediately upon direct irradiation by the laser. Based on practical applications, the threshold of soft damage to the detector is proposed.