In aerospace applications, a HgCdTe infrared detector preamplifier circuit yields the normal output at room temperature; however, it exhibits oscillations when the temperature is reduced to -55 ℃, and these oscillations intensify when infrared light is irradiated to the detector. In this study, this phenomenon is systematically investigated for the first time, and an equivalent circuit model of a HgCdTe infrared detector circuit after low-temperature irradiation is presented. The mechanism of the oscillation of the preamplifier circuit at low temperature is analyzed in terms of phase and gain margins. Based on the analysis, a solution is proposed to inhibit the oscillation of the preamplifier circuit after illumination at low temperatures. The validity of the method is confirmed experimentally.