The response characteristics of HgCdTe photoconductive detector have been discussed in detail. Several main laser irradiation parameters, such as irradiation time, wavelength and optical power density, are chosen to calculate response process of the detector. Based on traditional drift-diffusion model, an equation set with the variation of temperature is deduced to describe the semiconductor carriers’ dynamics features. Using the numerical method, the resistance and the output voltage of the detector have been worked out. The calculation results show that: thermal effect of the semiconductor detector materials become more apparent with the increase of irradiation time and the power density, but not much changes with the wavelength. The output voltage increases with the increase of power density, and eventually become saturated.